Lateral work and transitions on the flat will help put your horse on his hind end. Using gymnastics over fences will encourage your horse to use his back over the jump rather than just lobbing himself over it, this helping the front wnd stay tighter
gymnastics, start easy (one , two , three strides) and work your way up to bounces over small fences then increase height. he'll have to pick up his feet or he'll be hitting everything! lol
You can also do placement poles before and after the jump 9-10ft. Or do a V jump. (You have your regular vertical with two poles forming a V at the centre on the vertical)
I do simple grid work with a horse that not careful like a bounce or a vertical to a oxer to a vertical . I also would add pole work to your ride to make sure the horse pick up thier feet all the time.
I have a horse who was super lazy with his back end. Perhaps this will work for the front. I set up poles on tires , not very high, or cavalletti. Walk, trot, & canter over them . It will help him pick up his feet .