Wow, such a ton of hard work, you did an amazing job here and well organized :).
I truly admire your resolve, especially for those pen control exercises as I often get bored with those pretty quickly :P.
The one and only thing I've noticed (and maybe this could be useful to you) is that your gestures often has way too small heads. I know those exercises are more about flow than proportions, but it's a good habit to make the measures as accurately as possible from the very beginning. Maybe it would help you to start from the torso instead and put the head a bit later, when you're more confident about its size. Starting from a bigger mass can help with adding proportions for everything else.