The credit score is going to tell them what they need to know, and you trying to press their subconscious buttons by showing up in a suit might even set off alarm bells.

As a matter of course, we have to bring the building up to code which includes ADA compliance (grab bars and roll in showers) and fire suppression/detection (fire sprinklers, alarms and lights, etc.).  

This is all especially alarming with the knowledge there has been a fire in the house before.

I know everyone's ears are ringing right now with alarm bells, but is rejecting them as simple as emailing them and letting them know they do not meet the qualifications? 

Assuming you're running a professional operation within the bounds of the law, then asking tenants to pay their rent is completely legitimate.The first time a tenant threatens to sue, it can be alarming...but believe me--at a certain point, you've heard these baseless threats so many times, and you're so knowledgeable about the relevant laws and your own rights as a landlord, that you become emotionally numb to most lawsuit threats (again, assuming that you're operating a professional business that's within the bounds of the law).I don't know about the energy audit, but it sounds like just some more blustering the tenant is doing to try to intimidate  you....if the tenant is responsible for the utilities, and they think their utility bill is too "high", the obvious response is: "you have total control over the amount of utilities you consume.

That code violation typically racks up fines at an alarming rate.

All that said the bigger hurdle is that in RI 5 units need a fire alarm and emergency exit lights  while 4 units do not. 

You have a legal obligation, as a bare minimum, to enter to inspect fire/smoke alarms are operational, furnace filters are changed, plumbing is functioning properly etc.     

I have less worry about vandalism now since the electricity is on, the alarm system is armed, we have window treatments, etc.  

I planned on hanging up bandit signs in the wee hours of the morning... well my alarm clock went off and I hit snooze and it never rang again and once i Finally did wake up I was upset at myself.