Hello.
I would correct the setup first.
The bar is too much in front.Have it very close to your shins (touching). It should be over the middle of your foot, which is a lot more back that most people think. Use your lats for this.
You are rounding your upper back. It is a legit way to do it for some high level pullers, but not too much for novice. Think if putting your chest up and get tighter. It might help to also keep your back flatter.
If you were in the room, my cues for you would be in sequence: get tight (lats, abs, grip), chest up, sit back, push the floor away.