For villain, based on 55 hands we have, he is a reg.

I think this is a fold. I think he doesn't have often full houses here because those are most likely being raised either in flop or turn. Same for straight. The weakest value had he may decide to raise on river is is imo trips of 4. However I think he rarely has those here because he wouldn't call a 4 on turn(he is a reg, not a fish) The only 4s he would call on turn are a 4 which has the fd. Those are removed on river though. He also calls turn with 43s(that's 1 combo on river). He might decide to call A4 or 64s because he has a gutshot + weak pair. I don't have the knowledge though regarding how the average reg at NL5 plays those hands here. Even if he did call it's likely that he might not have A4o because he might not call this preflop. People at micros on average don't defend often their BB vs BTN opens based on what I've heard(our open btw is not the usual 2.5x. It's 3x and this means that villain calls more tightly). I think we should not expect villain to have A4o pre here 100% of the time. I think we are very often against a flush when villain goes all in. Pot odds are about 30% here. I think we don't win anywhere near 30% of the time when we make the call.