Good distances are important no matter what type of jumping you do. I ride jumpers, partly because we don't have hunters in Australia and partly because my horse is not calm enough for it unless he's lost his love of working.
Canter leads are also important no matter what type of jumping you do, because if your horse isn't balanced he can't jump to the best of his ability. Flying changes are immensely helpful in a jump-off and/or to ensure you make your time and of course they look a lot cleaner than a simple change but they're not essential as such until 3' and higher, at least not in the jumpers ring.
To add my 2c you look a LOT like I did about 6 months ago, except you have a more stable lower leg than I had then. You also have a better release, mine was (and is) almost non-existent.
I am another who doesn't understand why you had that big block of trot in there at the start of your course. Is your horse strong? If not then you have no reason to be trotting parts of your course, trotting into your fences can be done at home as much as you like but there's no reason to do it at shows.
Staying in your two-point with your lower leg strong and your body in balance, for half a stride to a stride, is a great way of making sure you're not coming back too soon - but you want to be in more of a half-seat than a proper two-point. Do you know what I mean? I have a photo that I took of a top rider that illustrates what I'm talking about, excuse the huge feral watermark. That's my old deviantart account. The actual photo's on the old computer which won't turn on.
She's actually too far forward and unbalanced, see how she's at the very front of her saddle and leaning on her horse's neck? If she was more towards the middle of her saddle she would be much better off. It's so long since I took that photo that I can't remember how the horse took the jump, could have been an awkward one. Probably was, considering it was taken at a competition where the entries are invitation-only.
But what I'm trying to illustrate is staying off the horse's back for at least half the getaway stride, and you can gradually bring that back so that you're back in the saddle as soon as all four feet are on the ground, but you're not going to be restricting your horse's hindquarter and causing him to take rails as you move up the heights if you stay forward a little longer. Just as long as you're balanced and not throwing his weight onto his forehand, so that he can take the second element of a combination that might be as little as one stride away.