I actually had to do the math and that's equal to running your tub on full blast for 8 hours straight. 

I had something similiar with a tub spout that was slowly leaking into the walls for a month before catching it.

So today the tenant moved in a 15 lb dog that's old and has health problems.

If it was in bad condition, them paint over it.Forget the little things like knobs and handles.Depending on the condition in the bathroom maybe new floor and vanity/tub. 

As a follow on, Congress did not extend:https://apnews.com/article/joe-biden-business-health-coronavirus-pandemic-us-supreme-court-65d530199d4dd2c99b9839fcd9c22294WASHINGTON (AP) — A nationwide eviction moratorium is set to expire Saturday after President Joe Biden and Democrats in Congress worked furiously but ultimately failed to align on a long-shot strategy to prevent millions of Americans from being forced from their homes during a COVID-19 surge.

My sister is a health freak and my mother is 93-years old.

"Because it is a big investment and you really rely on it for your overall financial health"Maybe drop a vague hint about you hating to look for a new tenant......

Obviously health benefits and tax payments are factors.

They insisted on being able to install a hot tub and getting a dish mounted on the roof despite the lease not allowing them and me telling them no several times, etc.

It's expensive for a landlord to turnover, they may be liable for some of those health hazards you listed.