It sounds to me like it might be more important to you to keep your son from getting upset than to really fix this, but I respect your asking advice, and it can be fixed!
Deep down you know it actually is important to his health that he gets good nutrition before he's 20, especially vegetables, and he needs to learn how to behave at the table, and to respect his parent's rules and his mom's cooking. 7 years is a long time not to have to do these things. It's totally normal that he is putting up a good fight. But it can be done! You can do it!
If you really want this fixed, it's good your husband is willing to enforce, this will be a huge help to you, as he is the male role model. As with any discipline or teaching, you have to make sure you are a united front, and that one of you isn't sabotaging the other. Decide you are both on the same page, and act accordingly together.
This is what works in my family: We don't discipline directly for the not eating. You don't want trauma associated with nourishing yourself. But you should DEFINITELY discipline for any fits or tantrums. Don't let them escalate, address them at the first signs of trouble, and don't back down. Be absolutely consistent enforcing table etiquette.
Footnote on the tantrums, you can't enforce tantrums only at dinner if he's allowed to throw them at other times. Gage your system and do what will work in your home.
As for the eating, here is what works for me. My daughter was always a very picky eater, but has greatly improved, and never cause drama at the table, even if she doesn't eat much.
Take the vegetable of the meal you have chosen (one at each meal), make it as tasty as possible, garlic, seasoning, tiny bit of soy sauce or pasta sauce, whatever makes it yummy. Cut it really small, and just give him a TINY TINY amount. like three pea sized cuts of asparagus, or half a broccoli floret cut in pea size chunks. Basically one small bite's worth. You must give it to him first, while he's hungry. Tell him he has to eat that before he gets the stuff you know he'll eat like all the carbs and dairy and meat stuff. If he doesn't, he just gets water until the next meal and no snacks.
Enforce behavioral discipline for any tantrums, but don't force the food itself too much. Explain, "You do not scream at the table, etc" along with his firm consequence, but don't say, "You have to eat this," other than in an instructive way with no consequence. If he's calmly not eating, let him be and don't give him anything else.
Remain calm yourself, and never get upset in both cases. If he throws a tantrum, only address the tantrum. He won't starve himself. Before long, he'll eat the tiny green bite on his plate so he can get to the "good stuff".
You can gradually increase the size of the veggies and fruit as he's no longer scared of it, and knows the rules never bend. being consistent is essential, if you ever give in, you'll make the problem bigger.
Don't entertain any drama whatsoever about what you're fixing. If he's crying while you're cooking, address the tantrum right away with a firm consequence. Choose a good meal, stick by it, don't explain yourself, and don't let him boss you around.
One thing that helped my daughter was explaining what each thing was good for, even if it was totally random like, "Anything green gives you your long eyelashes and pretty hair and makes you have fun! It's very good for your body!" This would not have worked on it's own though, she learned she had to eat it anyway with the other table rules, but it made it more fun. Now she tells other people what to eat and makes up reasons why. She loves vegetables, and she used to be terrified of them.
If you secretly don't care what he eats, and don't want to face the drama, just tell your husband your decision and don't fight it. Your son is exercising control and winning the way things are now, and the fights aren't accomplishing anything. Best wishes and I hope you have peaceful family dinners ahead!