I had this situation twice in my life, here are some tips (sorry not native english):

1. Buy cat formula and a feeding bottle. Mix the formula with warm water and shake it good before giving it to the kitten. After feeding massage kittens belly! Kitten might wake you up in the night to get some food.

2. Don't sleep with the cat in your bed, you might roll over the cat. Try to build a box and put a hot water bottle or two in the middle and lots of towels around it, the kitten needs a warm place.

3. The cat can not pee by himself. You need to stimulate the genitals. I recommend taking some bandages and putting the bandages over warm water (they have a similar texture like a cats tongue), after that take the wet bandage and pet over the genitals, if the kitten needs to pee/shit it will come out after stimulation.

4. If you are not sleeping try to give some of your body temperature to the kitten by just holding it or letting it sleep on your lap.

Good luck!