Some cats just get too overstimulated with too much petting. This usually happens if you rub a cats belly, and then it will grab your hand and bite. I don't know if this is what's happening with Cliffie, that he's getting overstimulated. My girl doesn't bite but if she's in my lap and move to get up she groans and complains. I found that by telling her first before I move that "I have to get up now" she actually gets off my lap without me having to remove her. It that doesn't work with your boy. Any time you sit down have a string or toy with you. Then just play him off your lap, and I think he should be so distracted with going after the string he won't think of biting.
Keep his claws clipped every 3 weeks. It's sufficient just to take off the sharp ends and be careful not to cut into the vein. Reward with treats after you clip his claws.
Kittens learn bite inhibition from roughousing with their siblings and momcat from 6 to 11 weeks, so if he missed out on that crucial social development, he doesn't realize he's biting down too hard. Saying a loud "Ow" and "NO!" and then ignoring him hopefully will get him to realize he's bitten too hard.
"We humans are indeed fortunate if we happen to be chosen to be owned by a cat." -- Anonymous