Mold in HVAC and threats to sue. Nightmare Tenant.

[Omer S.]

Tenant says mold was found in the HVAC system.  I had the HVAC system cleaned chemically for mold as well all the ducts cleaned.  The HVAC cleaning person sent me pictures of the system and it look like it had mold in it.  The tenant is now asking me to send a letter stating the the HVAC system needed to be cleaned due to there being mold present in the system.  

The tenant is 2 months late on their rent and always threatens to take me to court for not getting this fixed.   Should I be playing along with this game or should I proceed with evictions and not take their threats.