SB vs MP, river bluff after turn aggression and doubled board

PokerStars - €0.05 NL (6 max) - Holdem - 5 players
Hand converted by PokerTracker 4

CO: 103.2 BB
BTN: 109.4 BB
Hero (SB): 128 BB
BB: 87.8 BB
UTG: 85.2 BB 31/9/2 over 82 hands...not much worth info

Hero posts SB 0.4 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.4 BB) Hero has 7♥ A♥

UTG raises to 2 BB, fold, BTN calls 2 BB, Hero calls 1.6 BB, fold
Argument can be made that this should be a fold and I agree, but when one is card dead for a while, is kind of hard to fold it in this conditions, even knowing it'll be played OOP.

Flop: (7 BB, 3 players) 8♥ 6♣ K♥
Hero checks, UTG bets 2 BB, BTN calls 2 BB, Hero calls 2 BB
So far, I think it is pretty straight forward...

Turn: (13 BB, 3 players) 5♣
Hero checks, UTG bets 2 BB, fold, Hero raises to 9 BB, UTG calls 7 BB
Here it gets interesting.
FD+SD OOP. I like my hand and I think it is worth a raise. I try to take it OTT, but if villain calls, I considered I was in good shape. I got the math wrong:
1: Against random, I am only 60%.
2: Against his particular hand, even lower.
3: I cannot find his bet/call range here. And this is the first point I would appreciate you help.

River: (31 BB, 2 players) K♠
Hero bets 12 BB, UTG calls 12 BB
Having missed my draws, after my raise OTT and doubling the K, I think the K matches my play and I decide to barrel again, making it look like a value and not a bluff bet.
I know he has to fold 1/3 for it to be profitable. But since I couldn't place him in range OTT, should I check/fold this spot, instead of betting?

I know this was a cheap hand, but it got me thinking and would like your thoughts on this, as the play I've made is something I usually do and it could be taking a bite on my bankroll, if is too wrong.