3,5$ 6max A6s bvb bubble midpair vs polarized bet OTR

you should ask yourself why do you want to call if you could bet yourself? His range consists on not many bluffs because you block the flushdraws he might bluff. Therefore his range tends to be polarized. What kind of hand could he calling 2 times and then betting? I think sure this can be a 3 or a t bet thats not many combos. These are as less comboes as worse 6x.

I would estimate his range to be on the river with like this.
Equity Win Tie
MP2 56.24% 55.66% 1.15% Ad6d
MP3 43.76% 43.19% 1.15% 66-22, A7s-A2s, K9s-K2s, QTs, Q6s, Q3s, J6s, J3s, T2s+, 97s-96s, 93s, 86s+, 83s, 76s, 74s-73s, 62s+, 52s+, 42s+, 32s, A6o-A2o, KJo-K2o, QTo, Q6o-Q5o, Q3o, J6o-J5o, J3o, T2o+, 97o-96o, 93o, 86o+, 83o, 76o, 74o-73o, 62o+, 52o+, 42o+, 32o

According to that and your reads that he is on the passive side. I tend to bet myself small to get called by worse hands and to choose a sizing that I like. If he raises you he got you beat and you can be sure of it.

Pre-flop shove could be a interesting move as well. Than he needs to fold a lot with ICM in mind.
Otherwise you could get a hard time post-flop with in mind you play out of position.
Post-flop seems fine. I would most likely bet a little bit more like 1,5bb out of position.

Cheers,
SDK1987