I stole this from someone else: I think Harry gets swapped while looking into a mirror *right before* his planned wedding to Lara.
I don't know if Evil-Harry goes thru with it or not though. It would be interesting if he did, and then Our-Harry is legally, but not actually, married to Lara (no wedding kiss).
Regarding the Grave Peril decision - there are a few, but one early choice could cascade & change other options.
(I'm just about to start work, so I'll use that as an excuse to think about it a bit more.)