T.H.
I always liked the theory by Love and Logic of "toys I pick up, I keep, toys you pick up, you keep." This way the 2 and 9 year old will get to keep their toys and have things to do and his will disappear. I know you said that you feel nothing motivates him and that can be hard, but I think you need to pick something and stick to it. I would not suggest keeping him from meals, but possibly putting him in time out and if excusing him from time out to eat if he's still there and then go back. Time out can be hard b/c some kids act indifferent about it, but I truly feel that with enough consistency they will soon realize that it's annoying and that they'd rather be playing. It sounds like you've tried a lot of things, but maybe haven't given things a long enough time?? Don't know.
I also like Kristy's suggestion of switching rooms, that might help too!