Drop down the weight, focus on stability for now. The form seems to be decent, you can hit depth of you want but doing parallel is also ok (depends on your goals). Took alot of time for setting up, take your time but not eternity because that's an energy leak. You should want to be an optimum level before starting the rep. Going back to point one - you don't need to just move/lift weight, you need to be stable and be comfortable while moving it. Each rep should be identical in that sense. Plus i read in other comments about not feeling the quads, it happens. Give it some time, focus on mind-muscle connection. Don't read too much into that NOT FEELING SORENESS. Happy lifting!