Hi, if this is a youngster the horn should be hollow. You may find a friendly local farmer will help you remove it as they do their calves. If you can cut it low enough it may grow in a different direction. My ram lamb (now deceased!) was always rubbing his off on the fence and they always grew slightly differently.
I would think you can get something to put on the stump to stop it re-growing. Can't remember what the farmer does, either applies something or burns them.
Hope you manage to get something sorted, seems a shame just to kill him for that reason. Having said that, if you can't afford the vet, perhaps sheep are not for you as they are devils for getting sick for no reason.