I can only offer ideas that worked for us. My younger son is a real crazy man. He didn't throw food, but after the table was set (which was sometimes 20 minutes before dinner was ready), he'd climb in his seat and start playing/banging with his place setting. So I started setting his place on top of mine. Then I'd serve his food into his plate after the blessing and hand it to him.
I also had to get tricky with what I served him first. I changed tactics a while back, and instead of making my boys wait until after the prayer to eat, I put salad or raw veggies on their plate while I'm finishing up dinner. They're allowed to eat as much of those foods as they want, and they don't have to wait! Wow, their veggie intake has really shot up! Before that, my younger son would hardly eat a bite or two per meal. And being allowed to eat when he's so hungry and can't control himself very well really keeps things quieter at dinner time.
I also discovered that dipping is SO much fun that he sometimes prefers to eat his salad that way instead of with a fork. We have 99 cent divided plates from Walmart, so I put some ranch in one divider and pile salad in the other (after I ask him if he wants to dip his salad) and he'll grab a spinach leaf or carrot slice, dip it, and eat it that way. Since your son doesn't like to use utensils, allowing him finger foods first might help him want to use a fork or spoon on the foods that really count, like mashed potatoes!
My younger son hates being strapped into his booster seat. But if he won't stay in it (sometimes he wanders off), or keeps standing or climbing onto the table, I tell him that he needs to sit or I'll buckle him in. After I made good on that threat a few times, he has really settled down.
I wonder if you could compare his behavior at home and at school in a discussion with him. I have sometimes asked my son, "Hey, are you allowed to climb on the table at Nursery?" He usually just stares at me, but I know he's listening. "Well, you're not allowed to climb on the table at home, either." For your situation, maybe ask him if he uses a spoon at school (if that's applicable) and ask him to show you how he does it.
Good luck!