You don't want to defend 50% ,you want to defend vs his 3bet range ,if he 3bet you SB vs MP (let's say 3%) -you defend only JJ+,AK - 4bet KK+ ,call JJ,AK , let's say he 3bet you 7% and fold 50% vs 4bet (you defend with call 3,5%+3,5% with 4bet ,-if he's calling 4bet you start 4bet top 3,5% of your value range) ,if he's playing fold vs 4bet and 5bet you 4bet KK+,AKs + call shove and 4bet bluff KQo,ATS,KTs,A2s-A5s and call with 3,5% AQo+,JJ,QQ,KQs,AQ,AJs- if he fold more to 4bet you start add more hands in 4bet bluff range- your worst hands from calling range like Ajs,KQs,AQo. etc.As you played you can try a value bet R i think you get called by AQ,AK

I think pre flop is whatever, but call is fine. You are effectively playing 5 handed, so you are in the CO and the 3b is smaller. He goes 3bb to 8.5bb, so only need to call 5.5 and you are IP.

Yeah flop I think I check back as well

Turn is where I disagree. I think I would bet here for thin value/protection. You say your hand is not that good so there isn't a whole lot to protect. That is kind of the point with a thin value/protection. You typically have a marginal hand that is probably the best hand at the time, but very vulnerable. Any 2 over cards villain has ~12% eq. So Just with that, if you bet and they fold you are folding that equity out and if they call with AK, AQ, AJ, KQ, KJ etc then you got thin value from that, as you are IP, and can just check back the river. There is one other part with the protection. What happens when an A, K, Q, J, or T comes on the river and they bet. You probably fold, but you don't know if that card actually hit them or not. They could have AQ and a K comes and they bet it, cuz it looks exactly like they have AK, and you fold, but now you folded the best hand. Not even sure how you calculate that bluff equity. So I would probably bet the turn for 1/3 for thin value/protection. I guess it kind of sucks if they raise you, but what would they be repping really. The only other part that sucks with betting turn is if they opt to donk the river a lot. You could get put into some pretty tough spots like that.

As played, I agree, bet river to get calls from A highs. So again probably just 1/3.

Pre: Maginal but ok - I would expect to BE or slightly win with the call here - it really just depends on how bad villain will play post / how good you will play post

Flop: yes check back is quite standard

Turn: Checking back again is OK - so is protection betting for like about 40% pot - I'm leaning towards betting about 40% pot - we kinda secure that the river will quite often go check check - and we just aren't beat that often - and well we can certainly deny some equioty

River: Yup just vbet for about 33% and get called by AK high all day long

I'd bet turn after villain checks twice and I'd check the river if called this time, sometimes I'll bet bet if I have nothing though. I bet turn because, well, just so many cards can hit the river that I wont like, particularly any overcard at all and any diamond so I'd rather deny them the chance to hit as mentioned by the mighty fawltyfelix

As played, I agree with both previous posters that we'll see overcard type hands here enough times to bet.

Disclaimer: I'm nl5, 'nuff said.