Have you considered hook training? Basically, whenever you go to pick him up, you tap/nudge him gently with the hook to "snap him out of it", then pick him up. Usually I hear about people doing it for aggressive feeding responses (usually the bigger guys like Burms, Retics and boas) to give them a heads up that they're not reaching in to give food, but it might work with general aggression too. It can be done without a hook (like say, with a paper towel tube or something) but the added bonus of a hook is having something to pick him up with as well, just in case he decides to try an ambush attack.