str8 IP vs complicated board

PokerStars - €0.02 NL (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4

CO: 64 BB
Hero (BTN): 155.5 BB
SB: 68 BB
BB: 198.5 BB
UTG: 101.5 BB - No stats, but noticeable donk from a couple of showdowns already done).
MP: 179.5 BB - 96 hands, and playing 54/10 with AF=1

SB posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has 8♣ 9♥

UTG calls 1 BB, MP calls 1 BB, CO calls 1 BB, Hero calls 1 BB, SB raises to 3 BB, BB calls 2 BB, UTG calls 2 BB, MP calls 2 BB, CO calls 2 BB, Hero calls 2 BB

I think on the BTN, in a loose table, this is a no-brainer.

Flop: (18 BB, 6 players) K♠ 7♥ T♠
SB checks, BB checks, UTG bets 1 BB, MP raises to 6 BB, fold, Hero calls 6 BB, fold, fold, UTG raises to 11 BB, MP calls 5 BB, Hero calls 5 BB

Not much to say. If someone is to fold this 12-52, is better to fold it pre-flop.
My only doubt would be with original raiser (BB) possibly raising here. If such, I'd need to re-evaluate, but don't know how.
The 3-bet from UTG didn't really change much, mainly because of the bet size. Anything less than pot, in that context doesn't sound as set deffense, worst case scenario, he is running also.

Turn: (51 BB, 3 players) J♥
UTG checks, MP checks, Hero bets 40 BB, UTG calls 40 BB, fold

I'de preffer it to be a 7 completing my str8, but I have to work with what I have.
The board is messy enough as is. If I could take it now, perfect. Less bad, I ended up 1vs1.
But I narrowed the villain's range to AQ, QJ, KJ... and some FD... those kinds of hands

River: (131 BB, 2 players) 5♠
UTG checks, Hero bets 64.5 BB, UTG calls 47.5 BB and is all-in

If only the deck had 4 suits:f_rolleyes:
I honestly thought about checking behind and if it wasn't NL2, I'd probably would. And this is the point of me sharing this hand:
1- Outside NL2, is this a bet, or a check behind, without info on villain?
2- In the long run, how much is a check behind here costing me?