Make sure your tenants are making other arrangements, either on their own or through the Red Cross (their Renter's insurance should provide them lodging, and, if they caused the fire, might handle some/all of the restoration).

Rather than worrying about whether or not it is a violation of building code, I'd work on figuring out how to fix it before it causes more problems. 

Does this cause any problems with taxes if i'm writing off most of what I'm spending for the renovation?

A treadmill doesn't cause a ton of noise/vibration/shaking.

Working before closing without property insurance is risky (stupid); we had a major pipe break caused by one of our contractors that cost us thousands Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

Don't feel beholden to one, cause they don't to you.

Since you are not in a hurry, I would pretend the delay is causing you grief but that you are willing to give him another 15 days.

It cost us $125, but caused us no stress thus far.

This causes a lot of homes to sit on the market for a long time and the longer they sit the better the deal you can make when you buy!

I do know that in California with recent changes many of the "programs" for addicts had funding reduced, causing some of the larger ones financial problems.