i. Heine isn't very resistant, I guess, but the inside is like whoaaaaa ewww little kids killing each other and almost complete chaos under the immediate thoughts, and he has a separate persona of sorts that's even more Ax Crazy than him. As for Hades, he's pretty open in a way - you have to start thinking like him if you want to understand the inside of his mind, and... that might take a bit of work. even after she's 'in,' Hades's mind is probably pretty much impossible to understand.

ii. Heine: possible! might take a bit of work, though. Hades: nope.

iii. Heine: ahahaha they have already tested this. fall down, get back up, get even more pissy than usual. Hades: No effect. XD

iv. heine: not really? he might recover a bit faster, but other than that, no. hades: uhhh. it's highly unlikely that any spells would actually hit him, because he can literally disappear/reappear at will to avoid them, but if he does actually get hit by one, it won't bother him much.