I have no guess as to breed; however, I have some concerns about your horse's jumping form and the way he uses himself over fences.
The first photo shows him with his forearm below vertical, and very loose below the knee with his right front. It always concerns me when I see a horse do something radically different with each front leg or be very uneven. He's making a huge effort with his back and head and neck, trying to compensate for the fact that he doesn't know how to use his front end.
Second and third photo shows some improvement, but the overall impression is the same - not a tight front end, uneven and loose, overjumping dramatically with head, neck and body. Third photo also shows him engaging unevenly behind - usually a sign of unexperience or a badly balanced canter on the approach
IMO, this is a horse that is trying his heart out for you but lacks the basic skills to do his job. If he were my prospect or brought in to me for training, I would spend a *lot* of time increasing his fitness and working on grids and gymnastics. He would not be jumping single fences or courses for some time. In addition, when he started back jumping single fences, I would construct them carefully, with rolled out ground lines and lots of filler, to give him every chance to see and judge where he wants to wear his fences.. I would not jump with false ground lines or no ground lines until I felt he had advanced several levels in his jumping ability.
You haven't posted a confo photo, but from the flat photos, I suspect he is straight legged behind. Fitness is extremely important for horses with this confo to avoid stifle problems. I would introduce hill work gradually and keep it as part of his routine.
Good luck with him, he has a fabulous attitude. A little training will go a long way with him