Do you have any stats from SB? In general, I would play bet-bet-bet line against a loose weaker player in this texture. If he is tighter, you cannot exclude JJ here, but there are only 3 combos left and can almost exclude QQ cause it will play 4bet/call most of the time especially in case of weaker players. IMO betting higher on turn would be better (pot size for example), you can earn much value against his middle pairs like 77, 88, 99, TT and JTs, QJs, KJs, AJs. OTR i would make a thinner value bet between 1/3-1/2 pot and if I got raised just fold and move on. Know your feeling, you called it and shocked by A5s or JJ, I am in the same shoes sometimes, playing bet/fold in these situations is not easy but before betting river just ensure yourself, you are in bet/fold mode now and release the mouse to avoid tilty snapcalls :)

I'd size up on both turn and river as he's a weaker player and folding Vs River xr as that's going to be hugely underbluffed

Size up both turn(2/3p+) and river, think what sort of range u’re betting and pick the sizings accordingly, flop size up is also reasonable, but block is fine

• I go for bigger size flop,turn and river. SB has so much Jx hands and middle pocket pairs.
• If you only have range like this OTR. JJ+ AJs, KJs, QJs, A5s and want to bet Jx ican call with AA, KK. If you check back river with Jx and only bet AA-JJ A5s you can fold AA-KK and call with nuts.