You have made your decision. (It is a good, sound decision)
What about giving the landlord your half-of-the-months rent and letting her/him know that you would like to be removed from the lease. (I agree you should borrow if you must)
I believe that you can leave without dealing with the financial part of the problem till cooler heads prevail (meaning his)!
So sorry you have this extra money complication. Good Luck!