I was going to add my two-cents, but Kayty did a wonderful, kind job of explaining and demonstrating things :) My first thought (too) was "Oh NO! HEADSET? :::cringe:::" haha... I was also going to say that your horse looks like it is working more willingly in the most recent pictures, but again - is clearly pulling on you as opposed to accepting the bit. You'll get there, though!
Kayty's pictures really demonstrate an ideal lightness of contact between rider's hands and horse's mouth - her horse is not straining on the bit like your's appears to be. I look forward to seeing what you can accomplish with this horse in the future - please, ask your trainer about "collection" as opposed to "head set"... if you're trainer can't point you in the right direction, then perhaps you should seek someone who is credentialed or accomplished with Dressage. Even if you plan to work at a lower level, proper dressage training will only help you and your horse, and will translate nicely to any discipline you choose in the future.
Even if you weren't asking for a critique, I think she did a really nice demonstration for you :)
P.S. If he has a problem with the cannon bone, why were you considering hunter/jumper with him/her? Or, is that why you chose to focus on flatwork instead?