If you can please post some photos of your hen, the prolapse, her poop that would be good.
You mention that she's laying eggs - are they normal hard shelled eggs?
Does she have prolapsed tissue all the time? You are soaking her daily and applying vetericyn - so is there exposed tissue? For the last month?
Hopefully with more information and photos we can give you some suggestions.
You mention a rooster and he's plucking out her feathers - are the other hens plucking at her feathers too? If you are trying to get rid of him and have no takers, then dispatch him. If you won't do that then house him separately and see if things improve.