Hey gin
Please buy some weightlifting shoes. You'd benefit a lot from the investment.
The bar is too high on your back. Get it lower and under the spine of the scaps so it's secure and you can lean over. Lowering the bar and leaning over more will help to correct the knees sliding forward. Check out Nick Delgadillo's video about bar placement on our YouTube channel. Fix the bar position and you'll find most of the other things you've been working on may be fixed quicker.
Upload where? Here?