I can see two options you have, either put him in his chair at the table and don't let him down till he has eaten at least a bit of his food. You probably won't get him to eat it all as he will be too frustrated by you constantly putting him back in his chair. It takes effort and patience on your part but can be really worthwhile.
or, let him sit on the sofa, but keep the tv off. And TV only goes back on when he has eaten whatever it is.
I have similar problems sometimes with Georgia, but its more that she wants to get up and down, up and down. She is a kiddy who literally will not sit still. And her stock reply is to tell me she is finished, so she can get down. I've started now telling her she can only get down when we are all finished, or else she has to ask to get down. If she gets down I just put her back on the chair.
There are lots of things kids dislike unfortunately and sometimes you have to chose your battles, because you need to be boss, but you also need to decide which battles are worth fighting. For me, sitting at the table is one which is definately worth it.
Georgia is allowed to eat a sandwich or toast, or tracker bar on the sofa, but if it requires a spoon or a fork, she must be at the table. That's our compromise.
Good luck