i feel your pain! My horse, who is strikingly similar to yours, had the same problem, but we may have finally solved it.
First, it took a long time, so be patient. Secondly, i am so lucky to have a farrier who works with me, and is patient with this process. i can’t say enough nice things about him.
We initially put clips on, and squared his toes. Nevertheless, he still managed to yank a shoe off on a weekly basis (this went on for months!). As he matured (he’s now seven), his way of movement changed, and that presented a newer challenge. For awhile, we seemed to have fixed it, but then soon enough he began ripping shoes off all the time. He’s still getting clips, and squared toes, but our amazing wonderful farrier has started shaving the heels off the shoes. Not much, mind you, but those millimeters make a difference. i may be wrong about this, but i think that’s called short shoeing. Some people may recoil in horror, but i trust the farrier completely-- he watches my horse move before he shoes him, and knows the slightest change in his feet.
Ask your farrier about shaving the heels off his shoes. In no way has it negatively affected my horses movement. This may or may not work for all horses, but it’s done wonders for mine (and my piece of mind!).
By the way, i am still keeping bell boots on him at all times, and am now only using the pull-on kind. He used to rip the velcro boots off, and otherwise mutilate them beyond belief. Oddly enough, his feet are wonderfully strong. i (on my farrier’s recommendation), put Rainmaker on his hooves everyday, taking care to go about an inch above the hoof onto and above the coronary band. The bell boots massage in the oil, and may be one reason his hooves are so strong.
Also, since it’s summertime and dry, he’s now on a Biotin supplement, as an additional measure. That will help strenghten strong hooves even more.
Believe me, i know what you’re going thru, and even if this solution doesn’t work for your horse, you’ll find something that will!
By the way… how often does your horse get shod? We’re on every four weeks. Painfully expensive, but i’ll forego things for me so my horse is happy.
Gotta run-- guess who’s getting new shoes today!