Can anyone give me advice on good questions to ask a loan company/bank/credit union to determine if they would be a good fit to build a long-term relationship with?

But I determined that the properties would appreciate and I could increase rents.

Once projected income is determined based on either actuals or a market assessment of comparables rent you then deduct all expenses, taxes, insurance, repairs, maintenance, property management & .... 

The algorithm used to determine which RE to refinance will include both its equity and the rate on its current loan. 

I have since determined that the partnership works extremely well and together we are far stronger.  

They're really the determiners of what you need and can perhaps point you in the right direction or help you take the right steps.

I won't reward that mentality with a free place to live.

IRS has indicated they would be generous in determining reasonable cause for penalty abatement requests if returns were not filed timely.Please see this post I made earlier regarding the March 16th date as well as the comment by @EamonnMcElroy regarding small partnerships.https://www.biggerpockets.com/forums/51/topics/816988-march-16th-filing-deadline-has-passed-late-filing-penalty-infoAs always, please consult your tax advisor to make sure your returns are filed properly. 

I've listened to tons of podcasts, know my market, and am finally mentally ready to pull the trigger.

IMHO how you differentiate your vacancies from others out there will be the determining factor.