straight on paired board

Either he has the goods or he outplayed you indeed. He couldn't put you on 99+ since you would most of the time re-raise. It could be that he put you on J10s+, QJs, K-Js, Ax and 22 - 88. You see that most combos are Ax and thus he might pursue his bluff. Your re-raise could also indicate you were on a FD and a pair on the board would definitely lower the chances of you having a set. In the end he is OOP and the only chance villain has now is making a bluff and the math in this case isn't so much different than having an actual hand and betting for value. That is, if villain thinks he can make a certain bluff size to you to make it profitable, he would not hesitate to do this.

In the end I would have called as well since the only hand that beats you are 99 looking to his range.

Hope this helps, good luck at the tables!

1) UTG has all 55+ in his opening range.
2) You should have 77 in your calling range from CO and it is not a mistake.
3) With our raise on turn we show we have a 7 and when the board pairs and villain bets I do not like calling. He will not do this with a missed fd as we've shown we have a straight.

Preflop is not a mistake. 77 should be in your cold calling range. Usually I would just set mine OTF and fold without a hit but since flop doesn't hit UTG's opening range so hard and we have gutshot I think we can call. OTR villain has 55,88,99,QQ,KK,AA and maybe some bluffs. I think we can call OTR.

I will disagree with you. QQ+ is not calling the turn raise with 4-to-a-straight on the board.
I do not think a bluff hand will call that raise either.

I agree with nitrol, UTG doesn't have QQ+ even if he calls OTT, he is not betting river. His river betting range should be like this:

Board: 9♦5♥8♣ 6♥ 8♠
       Equity     Win     Tie
MP2    88.46%  76.92%  11.54% { 99-88, 66-55, A7s, 87s }
MP3    11.54%   0.00%  11.54% { 7d7s }

And he might not have A7s and maybe 87s in his UTG op range, he looks tight.

Okay I think that sounds reasonable and I change my opinion ♠_biggrin:

We block 7x hands so most likely villain has FH? Then it is a clear fold.

We not only block 7x but he has only 87s (if loose A7s too) in his open range. We are not splitting there.

Villain will not open A7s UTG

It depends on how he constructs his ranges but in most cases he won't have A7s in his range. Looser player only will.