It is very simple. Don't try to overthink it.
Pretty coin.
I don't think proof are made from extra thick stock. The square rims may make them look that way. The OP coin looks plated.
Sorry. Just damage.
Not in this case.
I'm thinking someone brushed it by hand.
Yes. Both are large dates.
No. It's damage.
I don't think it has been cleaned. Looks like a normal circulated coin.
Separate names with a comma.