I need advice

I started my plants in transparent cups and bad soil. After plants reached about four inches I noticed roots hitting the bottom of the cup, and droopy leaves. I figured its time to transplant to a larger contaner. I had bigger pots ready with the right soil and when i was transplanting i attempted to remove the bad soil from the roots as much as possible and accidently broke off half of the roots. Can they grow in the new soil? or should I start over?

finish the transplant. I have broken roots before in my dwc. They have always regenerated roots. They will be in shock from the transplant for a few days, so give them a week or two and see how they do.

how much water should i add after the transplant?

will the droopy leaves recover?

just water as normal. the leafs will recover from drooping. they dont recover from brown spots or burns. watering is done until you see the water start to come out of the drain holes in the bottom of the pot. then it should be good for 3-4 days. check with your finger 2" deep for moister before watering. droopy leaves are also a sign of overwatering. it is better to underwater. they recover better and faster from underwatering.

use superthrive or other B1 and dont over water

you'll probably lose some leaves but that is normal as the plant uses energy from them to develop new roots. as others have said, give it some time to recover and see how the new growth looks and don't worry too much about the damage done.