Oh, regarding Harry's return, might there not be someking of resonance, residue, signature, or trace that'd lead to his correct worldline? Granted, there are likely a near-infinity of them out there, but there should be something that gives a clue about getting back
Author's response
That would be a fairly Star Trekish method of unscrewing the inscrutable, but a possibility I guess. Not one I think it's likely I'm going to explore.
I see this as a one way trip.