Poker Stars, $0.50/$1 No Limit Omaha H/L Cash, 5 Players

Hero (CO): $134.59 (134.6 bb)
BTN: $100 (100 bb)
SB: $162.89 (162.9 bb)
BB: $77.61 (77.6 bb)
MP: $49.42 (49.4 bb)

Preflop: Hero is CO with J 3 A 4
MP raises to $4, Hero calls $4, 3 folds

Flop: ($9.50) 7 2 9 (2 players)
MP bets $6, Hero

There's two ways to play it. Obviously we're not folding like a nit, and what we want to achieve is to make people fold better high hands that would split or scoop us. We probably won't even outdraw someone who currently has a pair for high, would need runner runner for that, so have to try to make them fold

(a) call, hoping that if we fill our low on the turn then we can bluff them off high on the turn betting (especially if the turn card fills straights)
(b) shove now, hoping they fold most of their weak high hands (and maybe some A3 hands that are ahead of us)

SPR is less than 5. I bet/raise/shove.
If SPR is higher (say 8), I flat, planning to bomb turned nut low.

Depends on the type of player he is because he most certainly has you crushed for high if you push on this board and he has overpair he is certainly calling.I think a call and then bluff at a straight card on the turn is much more believable.Also if he bets big again on turn and your hand does not improve for high in any way you can get away easier since he very well could have you drawing to a quarter.Calling here gives you much more info imo when you can see what he does on turn or you might consider folding on flop since you only have 4 invested and no redraw for flush.

Without reads, I think call is probably the best line. Yes, the PFR could be raising with air and fold if hero raised cbet, but I think repping a draw (preferrably something that's not just a low completing such as 5/6/8) that hits on turn/river would be a more effective line.

The board is uber dry (972 rainbow) unfortunately, so there's not lots of draws to rep (like a flush draw).

We have nothing for high and no real draw either. If I knew nothing about Villain I would fold (haha call me nit bc I dont care ), but reads and stats could change that to both a flat and a shove.

calling here to either take the pot away on later streets or to shovel money in when i'm 3/4rd

Pretty much.