Untangle my thinking

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

Hero (SB): 104.8 BB
BB: 272.6 BB (VPIP: 47.62, PFR: 0.00, 3Bet Preflop: 0.00, Hands: 22)
UTG: 151.4 BB
MP: 103.8 BB (VPIP: 30.00, PFR: 30.00, 3Bet Preflop: 0.00, Hands: 10)
CO: 112.6 BB
BTN: 100 BB

Hero posts SB 0.4 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.4 BB) Hero has A:diamond: Q:club:

fold, MP raises to 3 BB, fold, fold, Hero raises to 8 BB, fold, MP calls 5 BB

Flop: (17 BB, 2 players) J:diamond: Q:heart: 4:club:
Hero bets 10 BB, MP calls 10 BB

Turn: (37 BB, 2 players) T:spade:
Hero bets 19 BB, MP calls 19 BB

River: (75 BB, 2 players) 6:spade:
Hero checks, MP bets 31 BB

Preflop. I can call or 3 bet. The BB was calling 39% of preflop raises and I felt that I needed to get him out or make a bad call in a bigger pot.

Flop. Standard?

Turn. Should I second barrel here? There are a lot of 2 pair hands, sets and straights in his range.

River. Should i block bet? I don't think I should call his river bet

3 to 8 from out of position is rather small, especially at 5nl. I'd make it about 11-12.

On the flop I'd like the sizing vs a reg or in a higher stakes game but again i'd size larger here, like 13-14.

Turn, you can comfortably bet fold here, people just never raise your bet without at least two pair and plenty of worse hands will call. I like the size.

River, yeah you should bet or check fold as a general rule here. i'd bet fold again, like 21 or something. You can do highly exploitable stuff like this at 5nl to get thinner value or get away with a few of your chips when beat. You could even bet like 15. There are a decent amount of worse hands that could still conceivably call a bet, and two pair/set was likely to raise at some point.