I already am paying them for pest control, but they recommended sealing gaps in the home, installing a plastic barrier, and doing a termite chemical service.

He’s very handy, a chemical engineer by trade, and loves numbers. 

Not trying to be harsh, but it’s true.

Does the severe weather create limitations for finding GC's or hamper their ability to get work done in the harsh conditions?

Great flashlights and extra batteries that fit, super long extender ladder, korkers/or other brands over shoe to go over your steel toe boots, GFCI tester, moisture meter, a dog nose, an extender mirror, shovel to check foundation moisture, respirator as some properties have gross smells or chemical exposure, regular retractable tape measure forget the laser one, 5 gallon bucket, zip lock baggies, brown paper bags, putty knife, variety of screw drivers,Are you checking basements?

@Veronica Thomas I have them sign off on a checklist through docusign that has a check-in / check-out column (fans dusted, floors mopped, self-cleaning oven cleaned, shelf out fridge cleaning, microwave inside clean, toliet scrubbed inside and out, cabinets crumb free, no chemicals/furniture/toliet brushes/brooms left on premise, no large garbage items on street curb, etc, etc) .

Sorry if I sound harsh but take it like a big brother telling you this because he loves you.

That might sound harsh, but if they're never going to be able to pay market rent, you're just prolonging your losses with them.

I'd recommend you try again using chemicals. 

Working as an operator in a chemical plant.