Hello there,
A couple of things come to mind. I heard on the radio one day that most women when they are mad or really upset clean house. I have done that myself.
As for the in-laws home, any other adult children in the family that can help out with the cleaning? Not to insult your in-laws or anything but I would hire a cleaning service to come once and clean it up floor to ceiling, windows etc. After that it would be much easier to keep clean and if your the one cleaning, bring all your own products that you prefer.
My MIL cannot clean now and all of the SIL have families, work and have to clean their own homes so it was unanimous if it needs to be done we would split the fee for the one time.
The number one best way to avoid MRSA is to frequently wash your hands to prevent bacteria from spreading.
You do appear to show some of the signs of OCD but I would feel more comfortable if you talked to your Dr.
By the way, that was a great vent and where better to get it out then posting it here.
Kindly,
Kitt