The fastest car will not also be the cheapest and most reliable, no car salesman would be believed if they claimed otherwise, so they don't.

.- He has now given me the ultimatum  of either me and him finding a solution that is  "fair to both of us" or I move out.

Prevention is preferable over solution.

Spend about $5 on an a Iphone-app (like Turboscan) that can scan to PDF, pay apple for the Cloud (or the Turboscan app will not be real reliable when it comes time to storing or emailing your images ) I been audited 2 of the last 4 years and the only thing they ever got me on was missing or losing receipts

https://moneyinc.com/the-top-five-ibuyers-in-the-real-estate-industry/I was also going to suggest, as a potential interim solution to help you and your partner on the carrying cost, is to explore short term rental. 

I believe you will find a solution. 

See if you can get reliable client experiences from previous clients.

Wood bleach is a peroxide solution applied directly to the sanded stain.

Everyone will say watch out for triggering the Due on Sale clause, but that is so rare, and as you have already alluded to, the solution is just refinance. 

Big piles of excess cash is the solution to nearly all problems.