I'm playing at microstakes(1.5, 3.5) regspeeds, and a common villain for me is someone who'll play 70-100% hands OOP(mostly flatting), and still have a very low fold to cbet(0-40%), generaly leading out on the river(almost always). Rarely rasing flop(flatting top pair even on very wet boards, etc) or leading out turn, mostly waiting for my turn check and then betting river.What'd be the correct adjustment against this kind of play? These kind of opponents seem very common on lowest stakes, but I also don't see much of examples with likes of them in VODs. I view fold2cbet<50% as a leak, but I can't seem to exploit it.I'll describe my thought process of playing them, This is what I'm trying right now:

• Open less buttons, down to top 60%
• Have at least one overcard or a gutshot to cbet; unless I have a specific read that at this exact texture the opponent is more likely to fold than his usual. 
• Check back most turns and take his float if I hit my overcard on river; generally barreling if I hit the flop or turn.
• Fold the river unimproved. IDK if I should call w/ ace high type of hand. I'd generally call a river lead with a middle pair(despite overcards on the board), etc.

However, after running some equations on different hands, I've found that this approach barely makes up for posting a small blind with most but the top of my 60% range, and folding bottom 40% of my range will probably kill me.For example, a hand like K3o will flop a pair of kings or better in ~23%, and I'll have an overcard w/o pair in ~63% cases.  I'd have ~12.4% of hitting my by king the river. If it's a K3s, I'd have an FD in 10.9% cases, flopped flush in 0.84%; I could also pick up turn FD for another barrel, and having an FD will make me able to take his float more often.However, as I've ran some equations, I realized that if my opponent's also 3betting, say, 20%(it's a value range and I'm losing my minraise with most hands), my expectation drops. The less they fold OOP, the worse is my expectation, since I'm not getting that big blind. So against a 20% 3bet 80% flat(it's a _common_ occurence) 30% fold to cbet floater, with the above mentioned approach I'd be doing worse than +0.3bb/hand with a holding like K3o. Still better than folding, but not by far. This way I also don't set myself up to gain much value with my best hands, either; my turn bets are too straight forward.If I also fold trash against him, I'm literally shooting myself in the foot with this approach. I doubt the top value hands in my range will make up for the defecit of folding buttons and barely beating openfold with a lot of other hands. I've tried to estimate how well limping hands that don't flop well but are too good to fold, but I have no idea how to calculate opponent actions in limped pots yet.So I'm close to giving up on a straight-forward approach against these type of players. So I'm again considering barelling them, but I run into some issues:

•  While their range is overall weak, they also have strong hands there. It's not uncommon for me to see 2 checked streets(if i didn't cbet, for example), pick up a river middle pair while they lead, and to see they've flopped top pair. That happens at least once per 2 matches, that's for sure.
• Same for the times I do cbet, they will flat all their strong holdings, regardless of their vulnerability. If they have Jx on JT9s flop, they will flat 3 streets. And they slowplay all the nuts.
• Among these kind of postflop villains, they often don't 3bet that much. A common situation in the videos would be to barrel off an ace high somewhat wet flop, if flatted pre - because there's not much Ax in the preflop flatting range(they're in 3bet range), and a top pair is not expected to c/c on a flop with draws. So the flop flat usually means a draw or a middling hand that you can barell off. But with my opponents, all the aces are there. And they will flat 3 streets.
• With these factors, I have no idea how to estimate the EV of my decisions. Just judging from experience, it doesn't usually go well, even if I pick(as I hope) decent spots to barell. Sometimes they fold river. Sometimes I valuebet myself into nuts. Sometimes they herocall river with bottom pair or J high on my first bluff. Sometimes they pay for my good pair with this kind of crap.

In general, I seem to be doing bad lifetime(small sample but still plenty games) against bottom line bad players(who'd have 5%- ROI over a decent sample). That includes both very aggro players and very loose players. As far as loose floaters -I've tried to play back at them and raise rivers; barell; or, on the contrary, play very straight forward, but nothing seems to work.The only thing I've noticed is that playing standard with radical opponents(who do "something" waaay too much) is having the worst result. And most players at the lowest stakes are radical in some way. (hell, I've had much more comfort at 7's, where people have a fold button).I would be very grateful if someone described more or less in detail, what kind of lines you would take against this kind of opponent; both preflop and postflop. Would you have a limping range pre above 20bb deep?  Would you openraise bigger pre? If you barell them, what kind of betsizing would you use? How would you read their range on the turn in order to barell them, if there's a ton of hands there? Would you barell only additional equity like at least an overcard, or decide mostly by board texture(or if it's opponent dependand, how exactly?) If you barell them, how would their reaction to turn and river barelling affect your play? Sorry for a long post with a ton of questions, but I really need some help here.  Tried to provide a fairly specific opponent example, so the only varied factor in the provided opponent is the reaction to barrelling.