Fostering: 3 and 1/2 week olds, questions

Hello,
I am fostering 3 and 1/2 week old kittens and have some questions:
Background: when I found them, their eyes were covered in "mud". I soaked it off and puss came out and their eyes looked bad. At the shelter they got subQ fluids, dewormer and penicillin. At home they gat eye drops, and eye "goo" and doxy twice a day. They are confined to a bathroom with a litter pan with Cat Attract in it.
Questions:
1. They don't pee much when I stimulate them with a moist towel. How much should I expect?
2. They do pee (and 2 of them have poo'd) in random locations. When should I expect them to understand the litter pan?
3. I have tried some "gruel" (food mixed with KMR and smushed up). When do you think they will be interested in that type of food?
4. When is it safe to introduce a water bowl?
The foster mum's at the shelter all have different ideas on these topics and I guess you all will too, but I'd like to hear!
Thanks

The only question I can help with is the litter box. Make sure the sides are low enough for them to get into, and put any waste from any where else, in the litter box, so they get the idea that this is where to go potty.

just sprinkle some litter over any pee and sweep it up and put it in the box. Poops, too.

There are plenty here who can answer your other questions, I'm sure someone will be in soon.

Otto,
See? I never thought of scooping up some of the pee with litter and putting it back in the box! That is clever! Thank you.
The box I have is a tray from the 3oz cans we buy for our big cats. They can walk in and out of it with no problem.
Denise