Lubylol, does he really need to jump? I'm sure he'd be a lovely gymkhana type horse (not sure the age/height limits in your area, but it's worth a try) or flat-class horse. You could do some english pleasure, w-t-c, lower level dressage, fun classes such as costume/relay races/team games, trail riding, parades, showmanship...the list these days is endless.
I know it's hard to have an animal who can't do what you want them to do. It's hard to come to terms with the fact that some things just shouldn't happen. But if you want Cowboy to stay sound (if he's even sound now) you really need to look at your options and choose something else for him to do. It's not the end of the world if he can't jump, be glad he can be ridden at all. But if you want to preserve him, you really need to just open your mind a little and listen to what we're trying to tell you. Take him to a specialist, or a chiropractor. They can tell you what damage is being done, and they can also help you make him feel better so that he can excell at another discipline.
He's a noble horse to of done so much for you, and he's truely one in a million. But don't take advantage of his body, just because his mind is willing. It sounds to all of us like he's trying to gently tell you that he's hurting, and even if he just keeps on keeping on, it doesn't mean everything is perfect. Some horses will do anything for their riders, and I think he's one of them. But ultimately, that almost always ends up in a permanently lame, or, in some cases....dead, horses.
It's kind of like those stories about dogs that you hear from time to time. About how, when both the person and the dog is in jeprody, even if they're injured, or it will cause them pain (such as running into a burning house or dragging a hurt owner to safety) they'll just do it, without another thought as to what will happen to them, or whether or not it's safe.
Cowboy probably feels like when you're riding him up to a jump, you're asking him to keep you safe. And he does. Again, and again, and again, because he feels like he's helping or protecting you. Horses are herd oriented animals, and if he feels like you're a member of his herd, he's going to do anything to please you and keep you safe.
Do you really want to be asking him to do something, if there's even a chance that it's hurting him?
It's your horse, and it's your choice- I get that. But don't overlook what we're all saying. There is a reason that everyone is in agreement. There's something there, whether it's his back, or his legs, or his feet- that's just not right.
It's kind of like, when you see an elderly person walk into, say, a store. And he's bent over, with a hand gingerly placed over his lower back, and taking tentative, measured step. You don't have to know him personally, or have even met him before. You just know that he hurts. Somewhere. You don't know if it's artheritis, or scoliosis, or ostioporosis, but you know his back hurts. While at the same time, his grandchildren, who are with him all of the time, and are used to seeing the way he walks around- wouldn't even think twice about the way he moves. To them it's just 'oh, grandpa has always been that way' because he has. Atleast, since they've known him anyways. And they can't really tell if he's getting worse or not, because they're with him all of the time. Lots of grandmas and grandpas walk like that, so it must be normal. But it's not normal. And it takes a stranger to point that out.
Do you understand what I'm trying to say? I'm not trying to push you on the ground and stomp on you...I've done some pretty stupid stuff with horses in the time I've worked with them. It's easy to overlook something that you're used to seeing, and it's easy to just pull up your guard and not let anyone break through to you about what's going on.
Whether we're doing it tactfully or not (and honestly, I do think that everyone is doing a beautiful job at remaining helpful and not harsh or sarcastic) we ARE trying to help you and cowboy both. No one likes to see a good horse go because of mishandling, or because of problems that could of been corrected early on. I'll even venture to say that a lot of people HAVE been the victims of this, and don't want to see you fall into the same hole. We're talking from experience, not bad will.
Just, try to hear us out. For the sake of your horse, if no one else.
Everyone in your life is meant to
be in your journey, but not all of
them are meant to stay till the end.