Here's what I see -
It looks like you're trying so hard to do everything correctly you are making yourself stiff and forgetting to FEEL and enjoy your lovely horse. I would like to see you relax, concentrate on your horse and do what feels right instead on trying to follow a lot off contraditory advice.
Now, I will tell you two specific things about your position and try to clarify some things for you. First, the lower leg - the ear shoulder hip heel alignment IS a good guideline, as is lower leg at the girth. To make this really simple, you want your stirrup leather to hang perpendicular to the ground. In your photos, you've pretty much got that, what you could improve is moving your stirrup out to the ball of your foot, with the outside branch ahead of the inside, and the outside branch almost touching your little toe. This will allow you to stretch into your heel a little more and be a little more flexible. Next, think about putting then grip more on the inside of your calf and less on the back of your calf. Changing the grip will elongate the leg and rotate your toes more forward.
Take a look at your photos and videos and really look at your shoulders and lower back. You ride with a pronounced hollow in your lower back, probably from being told to throw your shoulders back and trying too hard and overdoing it.
I speak with some authority here as I had the same habit for the same reasons and it took me a long time to overcome. Ideally, you want to bring your pelvis back underneath you (the hollow back tends to push your seat ones back)' relax the small of your back, and stretch up tall in an erect posture rather than forcing your shoulders back and hollowing your back.
I will post back later with some photos to illustrate what I'm talking about if you like.
But remember - you're doing a lot more right than you are wrong, and you're a happy rider on a happy horse. You're the kind of student I'd love to see come into my barn - capable and motivated, and with a few little tweaks, ready to advance!