Throwing my two cents in – find the horse you need NOW, not a horse who MIGHT be what you need with 30, 60, 90 days, or possibly even a year’s worth of training, and even then it’s no guarantee he will be the horse you need. He’s young and there are definitely holes in his training if you’re having to teach him the canter and he’s 7 years old.
I’m 20 years younger than you and *I* would be scared to get on this horse. These days I’m just scared of getting hurt, because there’s nobody but me to take care of me at this point in my life. My parents are in their late 60’s, I am divorced and have no children- so I try to minimize my risks as much as possible.
SR is also right in that riding should first and foremost be FUN. For some people, riding a challenging horse is their idea of fun. For someone like me, it’s having a horse I know I can saddle or harness up and know that they’re going to basically be the same as the last time I got on them, and I don’t need to worry about too much in the way of silly behavior.