You've mentioned 'backwards causality' which isn't assumed in our one-box solution to Newcomb.

Only to rule it out as a solution. No problem here.

How comfortable are you with the assumption of determinism?

In general, very. Concerning Newcomb, I don't think it's essential, and as far as I recall, it isn't mentioned in the orginal problem.

you need to tell me where you think logical and winning diverge

I'll try again: I think you can show with simple counterexamples that winning is neither necessary nor sufficient for being logical (your term for my rational, if I understand you correctly).

Here we go: it's not necessary, because you can be unlucky. Your strategy might be best, but you might lose as soon as luck is involved. It's not sufficient, because you can be lucky. You can win a game even if you're not perfectly rational.

1-boxing seems a variant of the second case, instead of (bad) luck the game is rigged.