Raise flop with nutflush draw?

Don't overbluff against so weak players, this guy had called the limp and donked otf, you don't want to bluff against him

I would just call flop. By raising you probably isolate yourself against made flushes and sets.
OTT I think villain should continue betting his strong hands but I have seen a lot of slowplays too. You could xb but I don't hate stabbing him. OTR villain still could have some overcards with one spade so you have some showdown value.

I think you played this fine. If you check behind turn and then stab once on a blank river, I don't think you will get that many folds. His air hands will fold but those you would beat anyway.

i would checkback turn and river without hit.
I don't think you get enough folds and i see many slowplays there..

I like it as played, except turn where maybe we could check too, might be close.
I think raising flop would be a mistake and trying to bluff river too. I know it can be frustrating to see such a lame pocket at showdown but there's just no much you can do about it

Yes, I think checking back OTT seems as a right move.

Raising flop will mostly accomplish things you don't want, like folding out K♠:X. You very much want these kinds of hands in, not out.