Thank you all for your responses, I have been going nuts over here with this!

Deborah, DS does the same with just wanting to get down to play! Isn't it frustrating! And he also pushes his feet against the table to try and get out (we have carpet though, so all it does is push him up on 2 legs.)

Stacy, I think the straps on the booster seat have been a problem, but on the times I am not "locking" him down, he wants to stand and climb on the table. We are getting there with that one, I tell him, he can either sit or he is getting down. I do want him to eat at the family table with us. I don't really do the kids table either, plus I am sure all David would do would be run around, no sitting. We had stopped his snack for a while, I guess I need to do it again. The problem with not having something is that come meal time, he is a miserable bear and still won't eat! So maybe this is a phase and he'll magically come out of it in a few days???

Taygensmom, Thank you too! You are so right, this is definitely turning into a major control battle! It is just so frustrating to offer a fairly decent meal (most of which he used to eat plus usually one new item) and his say yogurt. Then if I tell him he has to eat some of one item first, screams for yogurt. Then just screams. So, give it to him? I did today...
This was the case for lunch today, I was preparing and he came in the kitchen, and grabbed yogurt out of the fridge. Before I even put his plate on the table he was asking, begging, whining and wanting nothing else but yogurt. I put down his plate and nope, just wanted yogurt. I gave a him a bit of yogurt and said he could have more if he ate something else on his plate, he ate about 2 bites of chicken nuggets (which is the only other thing he'll eat right now - and that in itself is driving me crazy, I just don't feel they should be eaten every day...) At least he got in his chair to actually eat something, right? And food went into him... There is just so much stress around eating right now, for everyone b/c he is not wanting to eat or only eat a little bit of something that shouldn't be the only thing in his diet...