My current occupation is a chemical sales engineer.

If there is a well house, tenants are tempted to store chemicals and oil near the well head.  

I would look on Vrbo and airbnb at other similar properties in your area to see if this is realistic.Then you have some money for maintenance and upkeep, consumables etc.I would put all this in Excel and see how the numbers look.Then you can easily adjust numbers to look at options like a remodel or full gut of the house.You mentioned a pool so you'll want to have a professional pool company maintain your pool to limit your liability on the pool chemicals being off and causing a problem for someone.

-Use some sort of sealant where the foundation wall meets the concrete patio-power wash cement-possibly apply a chemical cleaner-paint once dryAny advice this would be much appreciated. 

Don't use vacasa or evolve or other synthetic property Management companies.

So, do I roll the dice and keep it, get the sludge cleaned out periodically, treat it with chemicals and what not, or, should I move on and sell it? 

There is a tool that you run over the wallpaper that scores it and allows the wallpaper remover chemical to loosen the adhesive.

Get the bait boxes that have the dehydrating chemical in them.

It is chemically noxious and has a very strong smell. 

or a antimicrobial coating (I do not like chemicals)5 UV-C disinfectant lighting system.