You are an excellent rider and your horse is very talented. He looks like he would jump anything for you that you decide to put in his path. The two of you could really advance.
I hate to write this but I would suggest...gulp...that you lose about 12-15 pounds. Take a full year to do this, so it's healthy. Your weight is fine for lower amateur, but I could see this as the only impediment to competing in upper levels. The people you will compete with at the higher levels are lean, mean, fighting machines, and the judges may mark you down in Dressage.