As far as Chloe and Gwen, I'll copy paste my reply to the comment two places below yours:
The question of if MC can undo what he did (or if he should) is one that's going to be explored in a lot more depth in Act Three.
Original Chloe was not a nice person. She was angry, bigoted and at best an uncaring sister to Alice. So the question is: is it better to be free and miserable or enslaved and happy?
And no, the MC's age is deliberately kept as vague as possible so that players can impose whatever age they feel like onto him :)