I agree with what Taylor has suggested but also take a look at yourself. One of the most common mistakes from a horse is due to us! Try sitting back and really lifting your horse onto his haunches (of course not over exaggeratedly) then try the grid work which will help tremendously but always remember to fix yourself before looking at the horse :)
Try smaller fences in the trot so he doesn't run through the bit, if that's doesn't work go back to poles for a lesson or two and work on slowing him down in the canter or trot over them and apply that to your jumping :) good luck
I'd recommend a lot of pole work and grid work to help him become more aware of where his feet are. Ground poles and stride poles also help them judge if they're struggling to see it.
I had a horse that just got really cheeky when she realised our poles were plastic and could knock easily, so we swapped our top rails for lead poles. Hope this helps!