I plan on going to the landlord and telling him how "John" is making things bad, and if he would allow "John" to take his name off the lease and then give the landlord several months rent in advance
If you have a plan in action and you have a set date you could always try and find a sublet for the apartment. It would save you some $$ and you don't have to worry about the lease. If you live in a university town you could try and post something there - I'm sure that he wouldn't come across any postings there and perhaps you can ask for a portion of the rent or otherwise. Another option is simply talking to the landlord and explaining the circumstances of your wanting to duck out of the lease early, and if he has any soul you shouldn't have a problem.
From what I have learned men that are very controlling and possessive tend to evolve and become physically violent. So I think that you should get out while you can. Good luck!