Is fold good?

I dont fold sets. For 100bb that is

I think we cant fold here especially vs a fish that can have here AK KQ KJ type hands also we win vs 44 wich will be very often in this line.
But i understand you getting worried here because after big size multiway here ranges get pretty narrow if you have 44 probably fine fold vs reg but vs fish never fold

I would definitely barrel turn and river with no worries having this set, villain have lots of Kx combos to call, and turn you need protection vs 1 card flush draws and straight draws that will realize their equity for free if you just check.

Trouble with barreling is when IP jams our EV plummets.

I think either folding or calling river is fine. I'd probably call because pot odds are favourable and sometimes worse + bluffs overplay but don't fret too much

I don't know so much coz I'm still learning to play but I feel like I'm behind as hero on the river. ( if villain player is recreational then maybe perhaps not likely bluffing with missed flush draw).
I'm beginner and don't know much about solvers but feels intuitively that I don't have the required equity to call the river (don't know about player type too much but the 3 flush board on the turn feels like the value of my 3 of a kind has been reduced.
anyhow, for me as hero, I'm playing the same as original poster and folding on river once I face the villain betting 44 BB on river Street.