Id first be certain there are no teeth or mouth issues and if that all checks out...he's not going to starve himself. So what if he's clumsy with it, as long as he eats it. You shouldn't have to cut it up for him either. You are feeding him more than just chicken aren't you?
My dog has fasted HIMSELF for 2 days before, it doesn't hurt them a bit. My dog has been on raw for probably total of 2 yrs now and he still doesn't know how to pull the meat off by holding it down with his paw. If its a big chunk, he just puts his head close to the ground and knaws till a piece comes off. LOL
I know a man who got a rott that had never had raw. He put the food down(raw), dog wouldnt eat it. He picked it up until the next feeding. This went on for 11 days until the dog ate and he's been good since. The dog had been a bit overweight and he did loose some weight but he actually looked great...and when he got hungry enough, he ate.
You think wild dogs are like "well, there's a rabbit here but I dont really feel like rabbit. I prefer a pheasant so Im just gonna wait" LOL, no, they learn to become animals of opportunity and eat what they can when they can.
You have to be fair tho and be sure there's no health issue.