Don't worry about how much weight you're pulling on lat pull downs IMO. When doing wide grip let your arms extend all the way up almost to the point where it's pulling you up, then focus, and I mean really focus, on contracting and pulling down with just your back, completely leaving your arms out of it. Of course the arms will be worked inevitably no matter what but really forcing myself to think about using my back only helps me out a lot.
As soon as I start worrying about weight on LPD is when I start just jerking it down. I just like slow controlled movements , add a rep next time or maybe a small extra set, or even just slightly quicker rest time. Then when you will you made that weight your bitch bump it up.
Also maybe try alternating them with weighted pull ups , you can't beat those