To me this horse needs some basic ground training -- starting with you being able to work all around him safely. Kevinshorses has a good point that if it's not your horse, you shouldn't have to train it, but on the other hand, you don't want to get hurt either, so it's a discussion that needs to be had with the owner.
I would keep a crop handy at all times. When he lifts his back foot for any reason other than you asking him to move, you tell him no and force his weight back onto it by pushing or pulling depending where you are standing. You can push his butt from the opposite side, pull his tail or pull his head; whatever you need to do to change the weight and depending on the risk to yourself for a potential kick. He must understand that his feet have to stay on the ground at all times.
For his pawing, you can again force his weight, but I have always found that more difficult in the front. A firm no and pressure on the top of his leg to push it down might help. If necessary, smack him with the crop, lightly first and progressively harsher if needed.
In any event, if he actually kicks or provides a "I-wanna-kick-but-I'm-not-quite-sure-I-can-get-away-with-it" kick, he needs a solid smack with the crop on his back leg/haunch with your no and possibly and really nice big freak out on him, depending on his personality. Might be an idea to be close enough to the tie to be able to quick release and back him right away as well. No leniency whatsoever with the kicking.
I would watch him for ANY sort of behavior that is disrespectful. The pawing and kicking are only a part of it. Any time you are near him, be sure that YOU are the one dictating when he can and can't move. If you are moving hay or shavings or whatever be sure that he has to get out of your way, not that you are working around him. You must be the bully, not him.
If others are working with this horse, you all need to be at the same table.
Edited to add: agreed, do not stop grooming him. Discipline, then continue as before. Discipline as often as necessary and continue.