Sandy,
I was in a very similar situation with my last employer.... residents went all summer without working air conditioning, furnaces catching fire over the winter, broken sewer lines, flooding, code violations, you name it.
Sometimes, the best thing you can do for yourself and your residents is to walk away. Be sure to put your reasons for leaving, clearly and concisely, in writing to the property owner. What you decide to communicate to your residents is a much harder decision. Whether you decide to communicate anything to local code enforcement types is even harder.
Where I am, tenants cannot deduct repairs from rent, but they were able to find out that they could pay their rent into escrow with the court and leave (getting their money back from the court) if repairs were not made within 30 days.
I'm happy to share the choices I made with you, but am hesitant to do so in an open forum. I'll send you a private message, and you can reach back out if you'd like to discuss.