M.
Kids tend to do what they can get away with. My son loves the rare night when he's sick and can make me get up with him and head down to the kitchen for a snack and a bit of tv. On those occasions, he really has to be sick, and he's limited on the time - only 30 min. My son was also getting up very early 5am, b/c he thought he'd get more time on video games. We told him he's not allowed to even turn the tv on until 6 am, so he might as well stay in bed and try to go back to sleep. When my kids try to get up and be with us after bedtime, we take away privileges (we have a system of tv tickets for time on the tv and for video games, which they lose for disobeying), and they have learned that there is nothing to be gained by coming down for "one last hug", or "something I just forgot to tell you about my day".
What type of disciplinary actions are you taking to keep your son in bed? Or at least in his room? If my children are having trouble sleeping b/c they've fallen asleep in the car, or had a nap, they are still not allowed to come out of their room, and must be very quiet. They are only allowed to read a book quietly until they get sleepy again. Is your son hungry or thirsty? Maybe an extra snack before bed, and a night-time water by his bed will help.
You didn't really explain the weird eating habit. Maybe a doctor would be able to help with that.
Good luck.
M. B