Bottom Set with flush hitting river fold or call?

[robinmasters]

Live $1/2 NL at local casino

My Read : Villian was decent player but had been betting and raising on hand strength, ie he raised $7 with mediocre hands 109,KJ/Q/10, J10 and raised 15-20 depending on limpers with big pairs and AK/Q. he Flopped set of 3s and check called and min raised the turn on a guy in earlier hand .

hero (225)
villian (400ish)

Hero dealt 6 [img]/images/graemlins/spade.gif[/img]6 [img]/images/graemlins/club.gif[/img]
UTG calls $2,fold to who Villian raises to $7, hero calls $6, BB folds, UTG calls $5

Flop: Q [img]/images/graemlins/spade.gif[/img]J [img]/images/graemlins/spade.gif[/img]6 [img]/images/graemlins/heart.gif[/img] ($21)
Hero bets $20, UTG folds, villian calls $20

Turn 8 [img]/images/graemlins/club.gif[/img] ($61)
Hero bets $45, villan calls

River 4 [img]/images/graemlins/spade.gif[/img] ($151)
Hero checks, villian insta bets $75, Hero ?

Given his raise size preflop and flat call on turn I was positvie that he didnt have QQ/JJ in pocket and without a reraise on flop and his call on turn i ruled out AJ and AQ/KQ since he played top pair any kicker in previous hands fairly fast. Dont i hear from QJ on turn given the board? so i was left with K10, 2 spades or 109. The river bet felt like value given pot size and flush hitting . I considered the bet might not be value and just a weak bluff as well but couldnt really decide since i hadnt seen him bluff yet. was my river check horrid? should i have bet $55 as blocking/value on end and folded to a raise?
all comments appreciated