your saddle may seem a little low because of the bend at your knee, however, I see that you point your toes down for the full revolution. If you tried to level out your foot and keep your heel down a bit, the height may be better. Along with focussing on keeping your upper body steady, you may want to do a ride a week where you focus on your pedalling technique only. It is very hard to focus on more than one thing at a time, but if you choose one to focus on every ride, after a few weeks/months it will be second nature to you and you will be more efficient.