DO NOT put vaseline on an open wound or anything near there bum!!!!! It is a perfect breeding environment for bacteria, wash with dawn dish soap and warm water, rinse well and make sure he's completely dry before you let him go.
Sounds really freaky.
I think deworming was the right idea, you should repeat in about a week, make sure he's eating. If you are sure they aren't maggots (from fly hatch) then worming is really all you can do except making sure he's eating and drinking.