Same

I can't get in the right position despite my decent flexibility.

First day I pulled sump I set a 50lb pr when I pull conventional I fall forward or back rounds like crazy

Put a tape ruler ( the 36 inch ones or yard ones )
On your back put a little bit of tape so it sticks
And dead lift like that with very minimal weight until your form is perfect ( aka that tape ruler is moving or jabbing you at all )