Skyrim "purity" quest glitch *possible spolilers?

Ok, so i finished the companions quest line and i married Farkus. I asked him is there any jobs that need to be done and he told me he wanted to be cured. He follows me to get the witches head and after i get the head i cant give it to him. He just continues to follow me around and the only things i can say to him is did our store make moneg, have food, and train me. I need him to stop following me! I know the usual glitch for the purity quest is that vilkas is the the one who WONT follow you! I tried talking to other members of the companions and they wont offer me any jobs. I've played many hours since the glitch because i thought it might fix itself (silly me lol) and it hasnt. I'm playing on xbox360 btw. Please help me to get farkas to stop following me or help me find a way to give him the witches head in my inventory!

Thanks!!