Not that my opinion counts for a hill of beans because I don't have kids either (though I was one once), but I think I fall somewhere in between Danzig and DTS in my thoughts, Mark.
First off, I don't think you were too harsh-- the only privileges you took away were electronic entertainment ones, and frankly, entertainment is your reward for getting your necessary things done. And you gave him a set day of when privileges would come back, so you established a structure. I think discipline, fairly administered is a good thing, and also I think makes for a secure upbringing.
What I would encourage is making what he needs to maintain his entertainment privileges a set list-- where I think parents can sometimes be unfair is when they continue to add things onto the "you must do" list, without any reward or appreciation for the kid accomplishing the things they originally told him to do. You know, sort of piling more work on top of work. If there are other things he needs to do, find some other privilege that he has to earn for those things.
I'm a fan of not forcing kids to finish what's on their plates-- kudos to you for saying he has to taste the food, but not necessarily finish it (speaking as a kid who had an ongoing war with my mother over eating that eventually turned into an eating disorder, the less importance put on food, the better). Mind you, if he doesn't eat, and he's hungry later, you can either let him go to bed hungry, thereby teaching him he'll have to eat when the family does, or let him make his own meal (and clean up after himself)- the trick there being keeping things you don't want him eating late at night out of the house.
Though I would still make him stay at the table, even if he doesn't want to eat-- families who can manage to eat together should take advantage of that time together, I think, even if everyone doesn't finish at the same time.
The main point that DTS raised that I think is very valuable is to make sure to praise him for what he does right-- if he does a good job keeping his room clean, or whatever, be sure to tell him how nice it looks. DTS is right in that most kids do want to please (even as they're busy challenging authority) and positive reinforcement can work wonders. Don't treat the things he does right as "Well, that's no more than he should do"- make sure he knows you're happy about it. I don't think he needs stuff as a reward, necessarily, because I think that makes us connect doing good with getting things, rather than bringing some happiness to other people. Which feels better than getting stuff, anyway, it just takes a while to learn that for some of us.
And I'm a fan of allowances, tied into accomplishing chores. I did chores for my spending money AND learned a lot about managing my money at the same time- my parents were NOT an open wallet if I ran out of money. Plus it made me eager to get a part-time job once I was old enough.
(Of course, I was such a nerd growing up, I got punished by not being allowed to read books!)
My two cents (more like a quarter at this point).