Hero folding middle set?

Live $3/6. Table is quite tight in general. Seen Villain made a play pf in the BB and try to squeeze out over callers, but he folded quickly after he got called pf, bet flop and got raised.

Hero(CO): $ 2000

Villain(BTN): $1800

UTG+1 opened to $18. Hero flatted with 6s6h at CO. Villain called on the BTN. Pot Size: $63

Flop 4c 6d 8c rainbow. PF raiser checked, Hero checked, Villain bet out $30. PF raiser folded and Hero flat called. Pot Size: $123.

Turn off suit Q. Board 4 6 8 Q all rainbow. Hero checked, Villain bet out $70. Hero check raised to $260. Villain made a speech about he didn't understand what I could possibly have, and said it out loud that I probably didn't have a queen, and then he 3bet to $900. Hero????

Obviously middle set is a great hand, but other than pocket 4s, I am not entirely sure there are many hands that I am actually ahead of. In a single raised pot, I think the Villain on the BTN can definitely have all 4 combos of 57s and 3 combos of pocket 8s. On the flip side, I am still ahead of his 3 combos of pocket 4s. Don't think he would flat called with QQ on the BTN, so I guess we can rule that out. With me holding two 6s, there is no combo of 86s available. Not sure if 86o would be in his range.

With this particular relatively dry and rainbow board, I don't see him turning a hand like 85, 87, 56 into a bluff either. He could easily just called my relatively small raise on the turn and try to hit the river in position. On the flip side, not sure why he would want to 3bet me on the turn if he really had 57 or top set. Maybe he was trying to induce me to get it in on the turn?

Not sure if I would really wanna stack off with middle set for over 300bb deep, and I ended up folding. Never got a reveal, but at least he didn't show a bluff straight away. Is it too tight of a fold?