You should never ever resort to violence and you should never try to force feed a child,weather that's by physical violence,force feeding or refusing the child any other food for a long time any child psychologist worth they're Doctorate will tell you that!
Your Husband is losing control Worried and that's not safe around any of your DC,he needs to get some help with how he responds to whats going on at home.
There are parenting classes that you can sign upto,they're not all as condecending as the name suggests,some classes are for situations just like yours,they offer real support and you'll meet other families that are going through the same kind of thing,it's a good way to find a support group of people that understand what your going through and that won't judge.
As well as getting your DH some help and support and for you as well have you spoken to anyone about your son's issues with food?
It's more common than most people realize sadly but there is lots of help out there and alot more understanding amongst the medical community now when it comes to refusal of food by a child.
We've been through the same ourselves with 2 of our DC(we have 5DC)our DS and DD are both asd,it took a while but we were very patient and we kept things very calm around meal times and it's taken a few years with DS15 but he actually enjoys food now and has a very varied diet.
I was actively anorexic myself from the age of 7-16,I've seen the struggling to eat anything/having a dangerously limited diet from both sides as a child and as a parent.
You must all feel like your living inside a pressure cooker which can't be a happy place for any of you and going and getting some help is never going to be a bad thing.
I hope you all get some help with whats going on at home,I know how hard it can be. 