How do you believe these things interact?
I have an Alchemist that I am playing in a game who will soon be using these in combination. If I cast False Life and Ablative Barrier and then take damage how is that recorded? How will this heal when using Fast Healing via Spontaneous Healing/Healing Touch Discoveries?
...and to further complicate issues: the character also has the Die Hard feat and Lingering Spirit Discovery. So he can go to negative hit points and keep fighting. But... how does this interact with the non-lethal damage caused by Ablative Barrier?
Just pretend that the temporary hp from flase life isn't "temporary", and then how Ablative Barrier functions is clearly like normal. Except, some of your hp will go away when False Life ends.
So if you take 10 damage, you would instead take 5 lethal and 5 nonlethal damage. Lets assume False life gave you exactly 10 temporary hp. Then, you would lose 5 temporary hp, and have 5 non-lethal damage. Remember that non-lethal damage doesn't actually do anything until it reaches your current hp so it doesn't interact with the temp hp in any noticable way. However, if you had lots of non-lethal damage that was greater than your normal hp, but less than your hp with False Life, and then the temp hp wore off you would be left unconscious.
Temporary hp cannot be healed in any way, and once lost it is simply lost.
Die Hard doesn't interact in anyway. Spontaneous Healing and Healing Touch do not interact with Temporary Hit points either.
Temporary Hit Points
Certain effects give a character temporary hit points. These hit points are in addition to the character's current hit point total and any damage taken by the character is subtracted from these hit points first. Any damage in excess of a character's temporary hit points is applied to his current hit points as normal. If the effect that grants the temporary hit points ends or is dispelled, any remaining temporary hit points go away. The damage they sustained is not transferred to the character's current hit points.
When temporary hit points are lost, they cannot be restored as real hit points can be, even by magic.
I am in agreeance with everything you stated except about Die Hard.
Say I have 80hp and have taken 90hp worth of non-lethal damage. Would I still be conscious? Or because it is non-lethal damage would I be unconscious?
What if I have taken 101hp worth of damage and I have a 20 Con? Then I would be more than 20 points below my maximum. Would Die Hard stop functioning at that point and I actually go unconscious? (Since the character has Lingering Spirit this cap would actually be at 130hp in this example)
What if in both of the above examples he also has 1 point of lethal damage?
Dealing Nonlethal Damage: Certain attacks deal nonlethal damage. Other effects, such as heat or being exhausted, also deal nonlethal damage. When you take nonlethal damage, keep a running total of how much you've accumulated. Do not deduct the nonlethal damage number from your current hit points. It is not “real” damage. Instead, when your nonlethal damage equals your current hit points, you're staggered (see below), and when it exceeds your current hit points, you fall unconscious.
You would be unconscious.
Diehard only kicks in when your current hp is at or below 0. You can have full hp, but having nonlethal damage in excess of your current hp renders you unconscious.
When nonlethal damage equals you're maximum hp (not current total) you begin taking lethal damage from otherwise nonlethal sources.
Also
Staggered and Unconscious: When your nonlethal damage equals your current hit points, you're staggered. You can only take a standard action or a move action in each round (in addition to free, immediate, and swift actions). You cease being staggered when your current hit points once again exceed your nonlethal damage.
When your nonlethal damage exceeds your current hit points, you fall unconscious. While unconscious, you are helpless.
Spellcasters who fall unconscious retain any spellcasting ability they had before going unconscious.
If a creature's nonlethal damage is equal to his total maximum hit points (not his current hit points), all further nonlethal damage is treated as lethal damage. This does not apply to creatures with regeneration. Such creatures simply accrue additional nonlethal damage, increasing the amount of time they remain unconscious.
Healing Nonlethal Damage: You heal nonlethal damage at the rate of 1 hit point per hour per character level. When a spell or ability cures hit point damage, it also removes an equal amount of nonlethal damage.
What if I have taken 101hp worth of damage and I have a 20 Con? Then I would be more than 20 points below my maximum. Would Die Hard stop functioning at that point and I actually go unconscious? (Since the character has Lingering Spirit this cap would actually be at 130hp in this example)
If you take 101 (nonlethal) damage it's much the same as 90. Except where before you had taken 10 lethal damage and 80 nonlethal damage (10 of 90 was converted due to maximum hp) and were unconscious you now have 21 points of lethal damage, 80 points nonlethal and are still unconscious.
I'm not sure what lingering spirit is, but I don't think it applies since by your post it only appears to increase where you fall dead at.
The whole problem appears to be that you don't seem to be familiar with how nonlethal damage functions.
I am familiar with everything here. I am looking for other people's opinions as there are some clarity issues within the rules. This, actually has been an issue since 3.x as Die Hard and non-lethal damage rules haven't really changed since then. If you do not believe me then I welcome you to do a google search for "D&D Die Hard non-lethal" and take a look at some of the forum posts. Since Pathfinder didn't really clarify those rules at all we are left with the same issue.
So, let me get your opinion straight. I'm not saying it is wrong, I just want to make sure I understand your outlook.
You believe that the general rules for non-lethal damage overule the specific rules of Die Hard. In other words, you believe that:
1. Assuming the character with Die Hard has 100 HP and an 18 Con and takes 101 points of damage that they would be Staggered but could keep fighting until at 118 damage (or -18) and would fall dead.
2. Assuming the character with Die Hard has 100 HP and an 18 Con and takes 101 points of non-lethal damage that because this was non-lethal the Die Hard feat would not kick in and they would fall unconscious rather than being staggered? Is this opinion just because Die Hard doesn't specifically mention non-lethal damage as the reason your HP total is below 0?
Yes and yes. No, it's not just opinion. That's literally how the rules work. Diehard does not take into account nonlethal damage so it has no affect on it.
Should it? Probably. But it's not written to. And we don't have any clear idea of how it should work. You can propose a house rule, but you seemed like you were asking for an understanding of the how the rules interact. Unfortunately, Diehard doesn't interact with nonlethal damage.
Also, there is nothing specifically in Diehard that deals with nonlethal, thats why nothing it says can trump the general rules of nonlethal damage.
Die hard can by bypassed by Non-lethal damage if somebody want to capture you. But it's still an extremely useful feat, I currently run a cleric that simply cannot be taken down, quicken cure moderate wounds once I reach the negative hp zone + channel positive energy + move action to activate my trickery domain shadow clone, make me into some sort of giant unstoppable machine. I did not think it would have been that useful to take endurance + diehard, but I kept getting hit with use spells and breath weapons that deal a lot of damage. Sleeping in medium armor is also a great blessing!
Alright, well that IS the way it reads. I'm not certain it is within the spirit of the feat, though. I guess that is subject to opinion unless officially clarified. I wonder how many people house rule this. I will definitely be bringing it up to my DM just so we are on the same page regardless of what ruling he makes.
So let me make sure I understand how the rest of this would work:
If you take non-lethal damage while you have temporary hit points these are actually tracked serpately even from your normal hit points. Thus if the character has 100 hp and 10 temporary hit points and takes 10 points of lethal damage while he has Ablative Barrier up; 5 points of the damage would be converted to non-lethal damage (keep a seperate running total), and 5 points would be taken off of his temporary hit points.
If the next round the same character took 15 points of lethal damage, 5 points would get taken off his temporary hit points which would completely deplete his temporary hit points. 5 points would taken off his normal hit point total and 5 points would be converted to non-lethal damage due to Ablative Barrier (which is being recorded sepeartely). This would have effectively healed him for 10 points of damage that turn (5 lethal, 5 non-lethal).
Then if this character activated his Spontaneous Healing/Healing Touch discovery he would heal 5 points of lethal damage which would bring him back up to full hit points. He would also heal an equal amount of non-lethal damage which is being tracked seperately. He would then have 5 points of non-lethal damage remaining.
Is that all correct?
I also wonder what happens if the character has taken 101 points of non-lethal damage and then is granted temporary hit points. Would this make him become conscious?
...is this also a good time to mention that the same character has a level of Barbarian and can gain a buffer of Rage hit points as well? It gets complicated here, you see.