Yup. Completely. She makes her choices with the information she has; and they're still valid even though the Doctor held back one fact.
Exactly.

Yes. And it wasn't a half-assed, "I'm bigoted and I can't help it" apology, either. He's cruel and cold, but at least he didn't leave immediately-- and he could have.
And he actually left the final choice to Rory (so many lovely parallels with Amy's Choice) - Rory could have let her in.

I think the "someone else" is just that they're from the far future, not the fifty-first or fifty-second centuries, but way beyond that. (Or they could have the information from the Silence…)
*nods* And I think it might be Other People fixing things ahead of time - if they say it has happened, then it must happen...

And I can so easily see River/Melody making the PTB think it was her when it wasn't. (To protect her mother?)
Yes, that's it. (I have a promise to keep... WHAT PROMISE?)

Who kills him and why he walks to his death are two things I haven't been able to figure out. I'm looking forward to finding out!
I can see him going because it's a fixed point, and it has to be kept fixed. But I'm presuming there's more to it than that...