For not having an instructor, you ride beautifully. Below are some nitpicky comments that you can look at and then take another look at your video. Note, I'm talking about picky stuff, and I'm an equitation instructor, not a dressage instructor, so keep that in mind should you see some advice that goes counter to standard dressage riding. :)
1. If you have someone who can longe you, try some isolation exercises-- moving one leg, one arm, your head and body, etc, separately from the rest of yourself as you ride. You still have a little bit of a tendency to engage your entire body when all you need is a nudge of your calf or a half halt with one hand.
2. Your heels aren't really an issue, except that they creep up when you squeeze, which means you are taking your thigh and knee away from the horse and losing some effectiveness of your leg when you cue with it. Try stretching your leg down, then squeezing, to encourage yourself to keep that leg nice and tight against your horse as you use it.
3. As you move up in testing, start looking ahead in your movements and preparing yourself and your horse for transitions. While you don't want the horse to anticipate and jump into a transition too soon, you also want your horse completely ready for your cue so that he/she can be more relaxed and responsive when you ask for a change of direction or gait.
4.Your post bothers me a bit, but I'm not sure if it because I'm used to huntseat, or because of something you are doing. You seem to pop up when you post, while I'm more used to teaching students to post lightly, just moving your hips enough that you are off the back for a beat, instead of bringing your whole body up out of the saddle and back down again. Dressage horses eventually have really big trots, so my vision of a good post might not be a dressage rider's ideal.
These are a few tips to think about as you re-evaluate your own riding. Overall, I love how eager your horse is to do the test, and how happy and responsive he/she appears. I think you have very nice balance, and lovely soft hands. Your horse shows how kind you are as a rider by being willing and relaxed, even when an occasional bobble or mistake occurs. Nice job! :)