If we give him on the turn, Kx, Qx, AJ/AT/JT some club draws, I guess maybe a couple stubborn 7x, we are prolly close to 50/50 vs that range. How to play the turn depends on his tendencies. If hes gunna bet all his draws and floats c/c is prolly better, we definitely arent ahead of his calling range if we bet and im not sure that we gain enough back by folding out his equity. I also think it makes the river harder to play vs his draws because hell call turn bluff the river, but if we c/c the turn I think he just checks back the river (Which is why I dont like your plan of calling a blank river).

On the turn, if you strongly feel like he doesn't have a king (which I would agree with), I would suggest you go for the x/r, since your Q5 is not going to win against another queen. Of course, it's easy to say with 20/20 hindsight, but my point is that your decision on the turn is all or nothing, and you should either raise or fold. 

Because of the club draws, if I played this hand, I probably would have raised the turn. AK is also a part of our BB 3b range, so our opponent would have a very difficult decision on his hands if he has a queen, and we're going to get reraised if he has a king, giving us enough information to fold right then and there.

I dont think that any q will fold the turn after a 2nd FD comes down

Once again position position position and hand selection...ur watching to many tom dwan videos...those plays he makes are versus thinking players who r pros...my point is q5dd has little to no equity postflop vs someone who calls a 3bet in position...i get that ur trying to resteal but u should b very careful doing that w such a weak hand and as the BB....having said that u and i know that these players at these stakes will never fold 2ndpr/tk...u will never b able to bluff him off of that hand at these stakes....NEVER!!!...ur plan was to resteal but then postflop u flat twice....a check raise either on the flop or ott would throw up some red flags on his end... if ur going to steal or resteal pf u cant go soft postflop...ur basically telling him okay its cool to take me to value town on 2 or more streets cuz i dont want to lose my pf investment so ill just c/c flop and turn then check the river...if ur putting money into the pot postflop by just calling after u 3bet oop u look very weak...if ur plan is aggression this hand then be aggresive...in my opinion ur story in this hand is not credible...c/r the flop then reassess if he flats....i get that the k on the turn lowers the chances that he has a k in his range but that to me is ur excuse for not seeing the bigger overall picture....

Looking more at this hand it seems more and more like a x/f on the turn to me. Even though there are two K and we block one Q his range is still full of it. There are just not many draws in his range.

If his range OTT is something like:JTs, AhQh, AcQc, KhQh, AsJs, AcJc, KdJd, KhJh, QhJh, QcJc, AsTs, AcTc, KdTd, KhTh, QhTh, QcTc, Ac9c, Ac8c, AdQh, AdQc, AhQc, AsQh, AsQc, AcQh, KdQh, KdQc, KhQc, KdJh, KdJs, KdJc, KhJd, KhJs, KhJc, QhJd, QhJs, QhJc, QcJd, QcJh, QcJs . We have a poor 20% equity. And I even excluded all AA-QQ and AK assuming he 4b it PF.

Regarding hand selection. What hands would you choose for 54% BTN resteal?

Hm.. which ones do you have in mind? What do you think his (or optimal) BTN resteal defense should look like. I am personally using this ones as suggested in Donkr GTO articles: Dark blue: flat, bright blue: 4b

well Im not assuming he has a perfect defense strat picked out, just that I figure hell be calling AJo and ATo to your 3 bet a lot, and always calling flop with them

If we think he has a solid opening and defending strat, surely 3 betting as wide as Q5s cant be profitable?

Q5 is not a profitable 3bet resteal...he needs to b 3betting a lot more often and his vpip needs to b higher in order for us to b 3 or 4betting with garbage...u have to fight fire w fire not fire with a water gun...ull never win...as far as BB hands that r good to resteal with r any pair and anything suited or connected no more then one or two gappers...ur oop u need strength to make moves...from the co or btn is a different story...and remember dont fall in love with ur hand just cuz ur the aggressor and u hit 2nd pair...when he is flating ur raise and then ur bet u have to ask urself y would he b flating here...its one of two things hes either strong or hes setting up a bluff for a later street...and when u give up on the turn it doesn't matter if its for value or a bluff u have to ask urself if I make this call how big is the call im going to have to make on the river going to b and is my hand strong enough to make that call and if the answer is no its either time for a check raise or time to dump it and wait for a better spot....

Well, we need to have a (wide) flatting range with polarized 3b range. 

The defense range I assigned to him is 13% of all hands, so he is still folding 40% to out 3b resteal. Also I expect him to fold a bunch to my CBs. And as such making 3b resteal profitable. I agree Q5s might be a bit to wide. Here comes my question what range is optimal against 55% steal?

For comparison, this is an optimal blind defense against 35% steal from BTN suggested in Donkr GTO articles: