does he need to be in a brooder 24/7?
can I hold him? how long and if I do it too long how will this affect him?
can I give him food now or wait 2 days?
when will he start pooping? (prob when he starts eating but I want to be sure)
You can hold him/her. The only reason you'd need to avoid that is if you were ill. If this is a lone duckling, you're probably going to need to do a lot of holding.
It needs to stay in a brooder for a bit, but that doesn't have to be a formal thing. A container you can keep at a constant 88-90 degrees F in the very beginning works fine. You want to give him room to get out of the heat, and you can decrease the temp by about 5 degrees per week.
He needs water in his container, always. Duckling crumbles work best for me for food. There's nothing wrong with mash as mentioned above, but I don't have much luck with ducks eating it. That doesn't bother me since it degrades a lot quicker than dry food does.
You can dip his bill in the water, then set him down next to his water. Don't use anything big or deep. Ducklings can drown very easily. You can do the same with his food. It's best to do that when you first put them in the container, but you're already past that part.
There will usually be some amount of elimination in the first few days regardless whether they eat. That's from the fact that they absorb nutrition from the yolk.
It's going to be wonderful!!!
I probably wouldn't risk it. Most illnesses that affect humans aren't transmissible to ducks, and vice versa. Without knowing what you have, it's impossible to say if the duckling could be affected. If you choose to hold it, you should thoroughly wash your hands and arms first and not get it near your face.