Hero has position. Calling lets him see another card and villain's action. Call and evaluate.

Assuming villain checks, I'd check back non-straight cards and bet spades. I'm happy to see a free card in a protected pot with a ton of outs, and get to see villain act again on the river. I'd bet spades because I'd expect villain to bet better flushes. I think hero is ahead, and I'd want to get value from worse and single high-spade hands.

If villain bets a spade on the turn, are you still planning to go with it?

ETA: thanks for the thoughtful responses

You are correct. The fundamental theory of poker DOES NOT apply when people aren't playing poker!! You have revolutionized the game, sir. Was it in spite of, or BECAUSE OF the bullying?

Another pointless post

I'd make a tight fold. When a weak-passive beginner player bets oop on a 3-flush board in a protected pot, I think hero is drawing dead with a 5-high flush.

You are correct. Whenever you don't understand the point, it's because there was none.

If your takeaway from the FToP is that we should never bet if it will induce our opponent to play perfectly, then you are misapplying the theorem. If you don't play in a way that maximizes your EV given his hand then your opponent gains.

V1 is all-in and you definitely have to improve to win (we have the nut low). It's possible that your pair outs are live, which is really the only argument for shoving in order to get V2 to fold.
Scenario 1: V2 has a hand like A8/99. If you get V2 to fold, this could open up your 4-6 pair outs. If you just call, is it possible you make more money upon hitting the straight (3-4 outs)?
Scenario 2: V2 has a higher FD. I doubt we get a fold since villain would have better than 2:1 against a shove.
Scenario 3: V2 has a monster (88,33,22). Fairly unlikely given action, but you're not in terrible shape with the overlay from V1.

Just seems rather pointless to shove on the flop, due to the pot being protected by V1 and V2 not seeming to care about the strength shown this far and potential for you to reopen the betting.