Withholding the rent will only cause more friction and will only cause more bad attitude from your landlord. Do you really need him to be motzi shem rah on you. Do you really need him to tell the neighbors that you are NOT paying your rent? Is that really necessary? How does that help you or help your situation? You know your are using the property and you know he is due the rent except for the last month which you already paid for and for that you should give him a note saying you are using your security deposit or you have already paid your last month rent when you moved in. What he does is not in your control and really won’t effect you because if you look at the scenario, if you were called to court and the judge told he that your landlord wants you out, and you showed him the title or contract on your new house that would be the end of it. The judge would tell him, you are moving and he will just have to wait.
So again, why stoop to his level. Be a mentch and be matzliach that is what’s most important.