Alright, I don't think I played this particularly well. Should I have 3-bet this with position against the CO open? He is playing pretty aggressively. The table only went 4 handed a few hands ago, and he got those stats mostly at the full 6-max table.

Winning Poker Network (Yatahay) - $0.10 PL Hi (6 max) - Omaha Hi - 4 players
Hand converted by PokerTracker 4

SB: 82.8 BB (VPIP: 44.00, PFR: 24.00, 3Bet Preflop: 21.43, Hands: 27)
BB: 40 BB
CO: 104.2 BB (VPIP: 64.62, PFR: 53.85, 3Bet Preflop: 27.27, Hands: 66)
Hero (BTN): 246.3 BB

SB posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has 7 Q A J

CO raises to 3.5 BB, Hero calls 3.5 BB, fold, fold

Flop: (8.5 BB, 2 players) 9 5 A
CO checks, Hero checks

Turn: (8.5 BB, 2 players) 9
CO bets 8.1 BB, Hero calls 8.1 BB

River: (24.7 BB, 2 players) K
CO bets 23.5 BB, Hero calls 23.5 BB

I think I played this hand pretty lamely. Just completely passive, without a chance to win without showing up with the best hand. Looking back now, I wonder if I should have 3-bet pre-flop and/or bet the flop when it was checked to me. As always, comments for all streets are welcome.

I would flat pre as you did.

My standard is to bet this flop when checked to, I want to get value from his wide range. as played on flop I guess call turn call river. But i feel really meh about it

Against a 60% range your hand has 52% equity pre so 3betting is a little ambitious.

On the flop I like betting small. I always half pot in position on A high boards unless they are exceptionally draw heavy. I would bet this planning to call vs a check raise vs an opponent this aggro. If check raised I stack off on a heart, Q, J or T. Checking isn't terrible here though, without the backdoor fd or with less overcards to top two I am putting it in my checkback range. This is close to the weakest hand I want to bet call here so its a marginal bet.

As played the turn gives you little option but to call when bet into. You're beating his bluffs and you have outs against his 9s but you don't want to either get it in dead or raise and fold to a 3bet. River same. Clearly a call.