well i was going to recommend twitching him, but your mom refuses. what kind of twitch did you use on him? was it a metal one or a plastic one? did you use it on his top lip, bottom lip, or both? and does your mom realize that when you twitch a horse you're not hurting them, you're simply numbing them and putting them in a more calm state? we used to twitch my horse because he had some serious issues with his ears (previous owner was careless and put his cribbing collar on too tight and it caused some nasty embedding into his skin around his ears/throat latch, so he had some issues with people even touching he ears) and when we twitched him, he was totally cool about the whole clipping ordeal.
now besides twitching, you need to not feed your horse treats when you're clipping him, especially if he's is behaving badly. because then you are simply rewarding bad behavior, so stop giving treats during clipping, only give them after the clipping is done and only if he was a good boy. If he was bad, then no treats period.
what i also found w/ horses that are problem clippers putting a chain over their nose works out pretty well. the trick is to have both a chain over the nose and a regular lead rope attached to the halter in a normal way. hold your horse primarily with the regular lead rope and keep a lot of slack with the chain. when the horse acts up, pull on the chain so the horse understands that what they did was not ok, and then give them the slack back. (get two people for this, but you should probably have two people no matter what, just in case)
the best thing you can do is to keep working with your horse so that eventually getting clipped is no big deal what-so-ever. try to clip him once every other week, just getting random stray hairs, but not full on clipping the horse. this will get him used to the noise and hopefully your horse will be cool with clipping.