1. The Blind condition states that you get a -4 to Perception checks that don't rely on sight, and automatically fail ones that do rely on sight. Can you still "notice" an invisible opponent that is 30' away using Perception if you are blind? I'm assuming that the "notice" doesn't mean "see the shimmer of movement like the Predator's armor" but more "hear/feel/smell" that there is something there.
2. Base DC to "Notice" an Invisible creature within 30' is 20+Stealth (40+Stealth to pinpoint). Does that already take the distance into consideration? Would that mean it is a 21+Stealth to notice an Invisible creature within 40'? If you have the Unchained Rogue skill unlock for Perception so that you only take -1 for every 30' instead of -1 for every 10' (10 ranks) does that lower the Perception check to notice within 30' then?
3. If you have Blindsight out to 30' (but are blind otherwise) and there is an Invisible opponent 40' away, you have the same chance as noticing them as a normal blind creature correct (including the -4 to Perception)?
4. Greater Blind-Fight says you have to pinpoint an Invisible creature at range to avoid losing your Dex (and giving them a +2 to hit), and states that it can be farther than 30' (which is covered by Improved Blind-Fight) but doesn't give the details on what is required to pinpoint an Invisible foe farther than 30' out. Do we just add distance penalties to the normal 30' DC as in question 2?
5. An Unchained Rogue can Sneak Attack someone with Concealment (unlike a regular Rogue), but not Total Concealment. If you have Greater Blind-Fight so that Total Concealment is treated as Concealment, can you then Sneak Attack an Invisible opponent (or anyone with Total Concealment)?
6. Can you use Stealth to "sneak past" someone with Blindsight? Or would it be the same as trying to use Stealth against someone with Darkvision (i.e. automatically failing due to lack of "concealment")? (I'm just picturing the fight scene with Daredevil and the ninja that "masked their sounds" to fool his "blindsight" being the equivalent of Stealth vs. Perception).
EDIT: 7. Against Mirror Image, Blind-Fight is "accepted" as a way to ignore the spell effect for the favorable 50% miss chance due to the caster being "invisible". I've always wondered what happens to the images though when you "attack a creatures square" and miss due to Total Concealment. Do you automatically miss all the images too? Seems very unlikely that missing AC by 5 or less automatically destroys an image, but hitting AC without an issue, but rolling lower than 50% misses everything in the square.
1) yes, invisibility only affects sight based perception
2)that is just the invisibility modifier, afaik no other modifiers are being added in
3)that looks correct
4)seems right
5)id say yes, thats the point of the ability
6)if you beat their perception DC you get to sneak passed them, also darkvision doesn't affect your stealthing in general (unless you meant to say " Or would it be the same as trying to use Stealth against someone with Darkvision in the dark")
7)when you miss you miss everything, unless otherwise specified in the rules for the ability you are using
6) Blindsense yes, blindsight no. The latter ignores even invisibility within it's range (and very few possess it; there are also few ways to acquire it).