Hi J,
I hear your utter frustration. I have a couple ideas for you to consider...It sounds like your son is probably already in sensory overload when this happens and that something about eating is a trigger--the final stray. Is it worse at the end of the day/dinner time? Does/might any physical input prior to meals improve his self-regulation? How well does your child sleep? Our daughter, while still young would have major meltdowns with things that wouldn't be a trigger to non-spd kiddos and it would "look" like a major behavioral issue but was mostly spd flight or fight response which she really could not control behaviorally (because its innate). I got a clue from this forum that she had a retained Moro reflex and checked it out with OT and began treating that--which led to great gains. Figuring out better sleep was/is big for us too. Our OTs are our lifeline, so if you are not happy with them, maybe its time to look some more... I think one of the toughest things about SPD parenting is learning to distinguish when its a behavioral issue and when its SPD (so intertwined)... As for what to do, perhaps trying to catch an opportune moment when your son is calm and well regulated and explaining calmly that the abusive behavior is NOT acceptable even if the stimulus(eating) is really impacting him and then brainstorm with him what other things he could do to self soothe (headphones? lycra swing, deep pressure) and then do some "practice runs" when you pretend that the stimulus is their and he practices the appropriate response. Keep in mind he may not be able to do even this successfully or consistently if he's operating in chronic sensory overload. J, it might also be worth having him try musician earplugs (if he can tolerate them) to lower the sound intensity without impacting his ability to hear conversations, etc.
Sirena