Feather fall- "Feather fall works only upon free-falling objects. It does not affect a sword blow or a charging or flying creature."
I don't think it would let you glide, no. It appears to just instantly make you fall downwards at 60 feet/round.
Flesh to Stone- I'd say based on a statue that size. A Sunder check would work as normal, I think. As for reassembling, with stone shape and a Heal check, that sounds like it would work.
Magic Jar- I'd say so, since you do control the body and suicide is possible.
Antimagic Field- yes, it explicitly affects the caster.
Detect Magic- yes, but it does take 3 rounds and you would usually need to have some reason to suspect it was an illusion, meaning you could just disbelieve it in less than 1 round anyway. Misdirection wouldn't work, but magic aura might work if you managed to get it to affect something that isn't an object and the caster of detect magic failed their check. Perhaps cast it on the square where the illusion is?
I've been saving up a few spell questions. Can anyone help me with a few of these? :)
Sure we can.
Feather Fall & Levitation. If you have some forward momentum (like with a running jump) does this spell allow you to glide? If so how far and fast could you glide?
Not so much glide, as to fall with a bit of forward momentum. In all likelihood, you would move laterally at the same rate as you were before the fall. The rules state that a character falls 500 feet per round. For example, if you ran and jumped off a cliff for 30 feet (an impressive jump for most) then you would move out 30 feet, and down 500 feet. On the next round, you would move our 30 feet more, and down another 500 feet. This would repeat until something stopped your downward momentum (i.e., the ground or feather fall).
Doing this with feather fall would simply mean that you could move out 30 feet, then fall 60 feet each round.
Flesh to Stone. What stats do you use when attacking a person/creature turned to stone? I imagine they have hardness 8 for stone, but do they still have their standard hit points or do have hp based on a statue of that size? What if you want to smash of the stone head or a limb?
For simplicity's sake, I'd recommend using the targets original hit points along with hardness 8. That way, should the target be cured of its affliction, you know just how many hit points he has left for the injuries he's sustained while living as a statue.
And if a stone form is broken can it be safely reassembled before restoring it to flesh (maybe with a stone shape spell)?
Stone shape does not allow for fine detail, so the restored victim may come back looking like a "putty face." Using other spells (such as make whole) to fully restore a petrified creature could also work, allowing you to restore the petrified creature without any outward scarring or debilitating effects. I suppose you could also glue it back together, but I'd imagine that would only leaved you with a broken man.
Magic Jar. If you are possessing someone's body can you perform a coup de grace on them? E.g. fall on a sword or run a dagger across the throat.
Yes, absolutely. This makes possession extremely terrifying.
Antimagic Field. The description says it "surrounds you" and emanates (away??) from you, but does it affect you directly - that is, does it prevent you casting spells on yourself and neuter any active spells on you and magical items you are wearing like rings?
I've always believed that, yes, it does suppress all of your ongoing spells and magical items.
Detect Magic cantrip & illusions. Can this spell be used to foil any illusion spell just by concentrating for 3 rounds to identify an illusion aura?
It will allow them to detect the the absence/presence, power, and location of an illusion spell, but it is not undeniable proof that it is an illusion. I would consider this to be "interacting with the illusion" and give the detector a save to disbelieve, perhaps with a circumstance bonus.
Also can you cast an obscuring spell like Misdirection on an illusion so it has no aura? I'm not sure if an illusion would count as an "object".
Illusions are "effects." According to its target line, misdirection may only be cast upon "one creature or object, up to a 10-ft. cube in size." Therefore, you cannot specifically target the illusion as it does not qualify. You could, however, target the area in which the illusion resides (provided it fits within a 10-foot cube. I suppose you could conceal larger illusions in this way with multiple casting of misdirection.