777 vs river donk

a flush can be (should be ...) excluded because he didn't have the odds on earlier streets

That's not how it works! Maybe he wasn't getting direct odds, but he can still have implied odds. Also what about hands like Ax of hearts which he can all have? Or what about the fact that it's NL2 and people will happily call large bets with anything.

Don't forget this is still NL2 and 99% of players will call down way too wide against large sizings. People love chasing draws and they'll do it almost regardless of sizing. So please don't discount flushes here, because he can and definitely will have them here

Back to the hand itself: I still call here because we still have a good bluffcatcher. Guy seems fishy enough based on stats and stack sizes so there's probably a chance he'll do this with some two pair type hand that he doesn't want to check/call with, for example.

With such a drawy board we can always bet large with set to let villain chase draws. I like to bet turn large here again. River is a close one and I am not sure whether we should call but if called, make a note.

I totally agree with TJtheTJ that flush should not be excluded. He can have implieds, pair + draw.. Also this is NL2 and villain is playing with short stack, we can't assume he knows anything about odds.
Imo river can go either way. Villains line is often super value heavy so I prefer folding, but vs less than a pot bet calling might not be theoretically bad either.