re: Poker & $2 NLHE Full Ring: Set in multiway 3bet pot monotone flop
It's not a donk bet, they all checked around giving you the last action to close, so firing is more than fine.
You should never be folding sets though in general, odds
on someone flopping a flush is like 120/1 so unlikely and even if they do, you still have outs.
As played, callit off and be happy. I feel as played, with the check/check/jam/jam by both, someone might have a better set or flush but hey ho..you're never folding & just a cooler