1) You are entitled to your overpayment back--you do not have to pay, and the landlord is not entitled to keep, anything other than the amount called for in your lease. If your landlord will not voluntarily return the overpayment to you, you could sue him for its return.2) A failure to repair or correct conditions which affect "habitability," or the fitness of the rental premises for their intended purpose (residence) can provide grounds to terminate a lease without penalty. That is because something called the "implied warranty of habitability" obligates landlords to ensure that rental premises are habitable and usable. However, a failure to repair nuisance, inconvenient, or aesthetic problems--ones not rendering the premises uninhabitable--might provide grounds to sue for some monetary compensation, but would not legally justify early termination.One option--negotiate an early move out, including potentially allowing the landlord to keep and apply the overpayment towards what you would owe under the lease.