My suggestion is pay a reduced rent or maybe none at all.
23 years ago I rented a house where the landlord was not fixing things in a timely manner. The first issue was plumbing in the kitchen. Then the furnace went out. So when they ignored that I read through my lease agreement, I researched tenant rights, I documented EVERYTHING, all issues, all communications, all in person contact when there was, and then armed with that I went to our local court and filed for a rent escrow.
Rent money was now going to the court in an escrow account. 3 months goes by and I call them up and let them know that keys will be in their drop box and that the property has been vacated.
Long story short we both show up at court. The magistrate throws out their counter-suite that I broke the lease (magistrate told them there could only be a lease where they kept to their terms and legal requirements). I also get my three months of escrow plus 3 months damages. The damages was to offset the cost of electric heat that I had to run and pay for. I don't think the magistrate liked these particular landlords all that much.
If this renter has certain entitlements then the key here is to research that, setup escrow with the courts, and make sure EVERYTHING is documented. If this renter lives in a 1 party consent state to phone recordings I would install something like CubeACR on my phone and make sure to save all pertinent calls. In a 1 party consent state YOU ARE NOT required to inform them you are recording. Only 1 party needs to consent and that would be you making the recording.
I did this with my ex-business partner to force him into compliance with certain terms of our business separation. Next time azzhole don't threaten to kill me... I have it all recorded.
