The colour moire is so slight that all you need to do is add a Solid Color layer of shirt colour, set it to "Color" blend mode, and paint over the shirt.
I've moved this into @Brian's area, because it's not my field of expertise.
When you did the file recovery, did you use SanDisk's own recovery software? It's very good, by all accounts.
That sounds quite normal, yes. But they can vary wildly, of course. Have you read this?
It's very likely those dullards aren't doing their noise removal properly.
That is a VERY good question. Yes, the instructions seem to infer that it's 2000 wide for all photos, regardless of orientation. But do you have a way of confirming that? Do they have a help line or something?