AA42ss 3 bet pot hu OOP

3, 9 or 8 would also be good since we would be ahead of many vilain's 2 pairs combos

Line seems ok.
I would try to bluff catch most cards and Vbet only a 3 and A but not sure if its right

i like check on the river honestly. i cant think of many hands hat villain calls the river with. i feel like a lot of times u hang urself to a bd flush while by checking u invite a lot of his busted straight draws to bluff u off. on a rainbow board like 389 ppl often continue with hands like 8jtx or slightly worse. sets or two pair will raise flop or turn so hes most likely be drawing. and with the stack to pot ratio and u call 100% on he river anyway.

Half a pot bet = I don't know what to do
If you bet, bet bigger otf and ott. River is a check-call as if you bet worse hands will fold and better ones will call. So against flushes you lose anyway, but with a check you give him opportunity to bluff you.