Grids and gymnastics, don't even jump single fences for a while.
You also really need to work on your own release; in none of the photos is he using his head and neck appropriately to balance. A head on or behind the vertical over fences is a bad sign, and an indication that the horse feels restricted and can't use its head and neck naturally. It can also certainly interfere with jumping form - strecthing forward with the head and neck helps free their shoulder to bring the forelegs up.
While your horse can certainly be considered to hang in front, he appears to be athletic and is compensating by just jumping higher with his body and giving the fences more air, so at this time and this height I don't feel that his form is particularly dangerous. I would not be going up in height until his form improves dramatically though.
While I like gyspy's comment about improving the quality of the canter, the thing that jumping horses need most is to really develop their ability to shorten and lengthen the canter in balance. This is what helps them cope with a bad distance safely. So in your flat work, work on developing three, clean, clear paces at the canter, then expand to five.
Grids and gymnastics work best as a teaching exercise for the horse jumped on a loose rein, with the rider in a stable two point, just supporting with leg. You do not want to "help" through a gymnastic, you want your horse to develop their jumping skill by figuring it out without you.
Good luck, he is a good looking rascal.
ETA: I apologize, I realize after re-reading that this was not in the critique section, and that you asked for help and exercises, rather than critique. So I hope the above was helpful, and heavily weighted on the help and suggestions, and lightly weighted on the critique.
Last edited by maura; 01-26-2012 at 11:00 AM.