We have 4 cats...all abandoned ones that needed homes. 2 of them I found as 6-week-old kittens. One is now 15 and the other is now 4. It's hard to let the little guys go.

I've nursed unweaned kittens before and also had litters from my cats...IME they generally need to eat every 2-3 hours. Even if he is asleep, you need to wake him up to eat. Kittens tend to sleep while mom is gone, and she will come back to feed them every 2-3 hours, and they wake up once she settles down and they smell her. They're just like human babies, they need every bit as much care, right down to elimination (which you sound like you've got down pat). One thing you may want to consider is getting a heating pad to put on one side of his box so he can stay warm. Without littermates and without a mom, he'll be cold since kittens can't regulate their body temperature well. If you get a heating pad (or even one of those rubber ones you put warm water into), cover it with something furry or soft so he can snuggle and feel secure.

Kudos for helping the little guy out! We need pics!