"Part of me wants Ten II to be the Doctor, as otherwise Ten I has given everything up for nothing. And yet part of me cannot bear the idea that Ten II is the Doctor because in many ways for me that means that the Doctor’s grieving Rose ... was essentially for nothing, too (how can he have done that and then turned around and effectively dumped her, first chance he realistically had?)"

I don't believe he's given it up for nothing: he's given it up for love. Like the saying goes, "If you love someone, let them go"

I like to think that he feels he's giving Rose, and his human counterpart, the chance of a normal life together - something he longs for himself, but knows (or at least, believes) he can never realistically achieve with a human being.

And now I'm starting to cry again, just thinking about it.