First, the repair problem should be brought to the landlord's attention in writing by certified mail. You may end up in court and certified mail is the best proof of delivery. Second,as long as you are living in the house your landlord is entitled to rent, with some limited exceptions that don't seem to apply here. Remember that you can always negotiate. Discuss the matter wit the landlord after sending the written notice and see if you can lower the monthly rent even more.
No attorney-client relationship is created by answering questions in this public forum. If you wish to create an attorney-client relationship, you must contact me directly and sign a representation agreement. Answers are provided based on general ideas and an answer specific to your situation would require a review of all documents.
You can cancel the month-to-month by giving 15 days notice before the end of the period. So, if rent is due on the first, you can give notice so that the landlord receives it by August 15 sent certified mail and you can terminate as of August end. You can then move out the last day of August and turn over the key and not be responsible for any more rent. Take plenty of pictures before you move out.
Or you can do as Attorney Chen suggests and send a seven day cure letter. Make sure to get the proper form, then send certified and give the landlord seven days from receipt of the letter to fix the problem. State the problem specifically and in detail.