I'm guessing the creation of the Deathly Hallows came well before the founding of Hogwarts - otherwise Harry would have been able to control the Basilisk.
I think it would have been absolutely stupid for Snape to go down in some noble duel, even at 11 he knew he fancied "brains over brawn", as he put it.
I don't think the house of Slytherin is quintessentially evil, but as Harry says to Albus in the Epilogue, if you really want to be in a house, it's your choice. I'm betting that before Voldemort came into power there were not so many negative connotations and Slytherins would have been a more mixed lot, but upon knowing the kind of trash who landed in there upon a preferency for pure blood, who would allow the hat to put them in purely because of ambition or cunning?
Oh and that kid's name was TOTALLY not simply Albus Severus, I'm betting it's more like Albus Severus Sirius Remus Nymphadoro Regulus Kreacher Potter... but, y'know, it's a wee bit of a mouthful to say all that as the train is about to depart.
I lost $10 on Hagrid not dying, but I won $5 on The Quibbler/Lovegoods having more validity than it was credited for.
I think it was important for Harry to finally have a family, to have love. The epilogue was corny (and I could not stop but lol at Scorpius Malfoy), but I do think it improves with every rereading.
The Hermione thing may be a plot hole, but I like to think that there is a difference between wiping someone's memory and giving them completely new ones.
I'll even support the sillyness of Accio Hagrid - like Expelliarmus, Accio is a spell which has had proven success for Harry in the past and one of those he has real aptitude in.
I think killing Fred Weasley was one of the cruelest things she could have done, as it leaves George to run a JOKE shop. I know an important Weasley needed o die, but I think Molly would have had significant enough impact.
And this thread has sort of validated my belief that fan fiction has a way of ruining books. I liked it a lot.
Edit: I think that it would have made no sense for Harry to have mourned every death in DH - Dumbledore had told him for years that Death was not to be feared, as Voldemort had done, for him to be a sadsap over it through the whole book would contradict his actions later on - allowing Voldemort to kill him.