In regards to the shoulder-hip-heel line, I think that you are pushing your heels down, which is sending your lower leg forward. I am assuming that you want a dressage focussed critique. If that is the case, you don't need to push
your heels down. Let them fall down on their own. I used to have the same problem, my lower leg went forward because I was forcing my heels down so hard.
Also, your back is nice and straight, but your shoulders seem a little hunched forwards. They need to some up and back a touch. Try lifting them up, pushing them back, then letting them drop. That is where they should sit while you are riding.