Transaction volumes continue to be slowed with days on market increasing, but Sellers are remaining defiant and not coming off too much of their higher prices.

Interesting that this seems to cover all property zoned residential, with no apparent carve out for a transaction of residential property between two investors.  

This would be a prohibited transaction since you're a disqualified party and anything you already own (your LLCs) is part of that. 

Monitoring open windows isn't feasible in my case, but I can definitely monitor daily electricity usage online  

There are far too many regulations, the transaction is a much longer process, and we are talking about someone's biggest purchase.

I agree that DealCheck (or the BP calculator) does not provide enough tools or functionality to analyze those types of transactions (yet).But I would argue that it does a great job at analyzing more traditional buy & hold SFRs and multi-families, as well as flips and rehab projects. 

For instance, if you’re handling the strategy, guest communications, and daily management while the property manager focuses solely on physical tasks, you’d likely qualify—especially since your husband wouldn’t be contributing hours.

Funny, I was hoping to equip myself with some ideas so I could propose some transaction options to them right off the bat--but I agree with you that that is probably not the right move.

How exactly does transactional lenders work?

I would suggest giving it up and just hire an agent when you are ready to transact in the future.