Indeed, nice work Boomer!
And for the record, you asked:
How do you decide which images are salvagable?
It's been my discovery that EVERY image is salvageable, even if it serves to be a filtered-up background noise for some other piece. I try to throw as little away as possible, it can ALWAYS be recycled.
How do you decide which photos to work with and which are destined to become snapshots?
This all depends on your eye. For those that don't have it, it's difficult to tell. For those that do, just learn to trust it. You got it, trust it.
Once started, how do you decide when to stop?
Touching up a photo or creating a project can go way beyond the ridiculous as far as time is concerned. What I do is take a good look at the finished product every so often. If I like what I see, I save a version of it and then proceed to butcher it some more.
Cheers, and great work!