I would lean towards folding to the 3x UTG with AJo, even against these Villians.

As played, I would definitely check behind on the river. What better hands fold?
AK splits
Medium pairs are counterfeit
He never folds a T
Might fold KK/AA, but I wouldn't count on it.

If you want to make a move, I suggest you do it on the flop.
He's going to fold a decent amount, and even if he calls you have 1 over, a gutshot and J might give you the best hand.
It also gives you the oppertunity to check the turn, and you have initiative.

If you raise to 15 on the flop and he calls, the pot is 37.50, and he's going to check the turn, so you're off cheaper than the 41.50 in this case, plus the initative and flop folds I mentioned above.

This is of course a play you don't want to make against anyone and on any flop, but there are definitely good spots for it. The worse the player, the more tempted I'd be to do this, because Villian might not realise you only really rep Qx for value.

I don´t think flat this is a good rule of thumb ever. The BTN could still squeeze and you are in a shit position, or even call IP and will be very bad to play your AJo 3way in a sandwich. So for sure I would 3bet or fold this. 

As played, agree with Sonnen and I wouldn´t bet never here. 

I wouldn't call here if it wasn't for a fish being on the button and the blinds seeming to be pretty bad.

In hindsight I agree with you that my river play was bad. 

Raising the flop seems very interesting. One argument I have against it is that I'll mostly only fold out hands that would have given up OTT if I just called anyway. Though getting to check behind turn and be sure to see the river if we raise the flop is somewhat appealing. 

I find it hard to evaluate which play is most +EV in spots like these, calling the flop or rasing.

Obviously it's player dependent but let's say against a seemingly descent reg like this one. 

Any ideas?

I prefer the flat OTF and would do so with most of my range. You can probably get away with raising an unbalanced range weighted towards bluffs coupled with some nuttier value hands but I don t think that s the best way to play AJo. You nearly have the nut 1 pair and you can probably take him off underpairs and AK later if you feel that is necessary. I d rather raise with crappier hands.

I agree with the others that flatting AJo here is an error and a fishier button and maybe badish blinds doesnt make up for it. The fish still has position on you and your going to be guaranteed the worst relative position OTF. Oh ya and your potentially inviting a squeeze :(.