Given these factors, would it be worth refinancing for a lower interest rate (3.75%; 30-year fixed)? 

You were never cash-flowing $1200 to begin with.When you factor in vacancy, CapEx, maintenance, property taxes, insurance, etc it adds up.

Do those unrelated expenses get factored into the NOI?

My intention is to understand the trending areas within the country and the factors that are motivating the population increases/decreases throughout the nation.  

@Laurent Meyer no matter what you think of the motives behind the media, government, etc... regarding the pandemic the fact is it is having a real impact on people's lives, their lifestyle and their earnings.

If not, then Refi and restart your 15 with about the same terms and for 8k getting 700 less on your payments.This is a life style choice over a what's the math says choice.

With that said, how do you account for this factor, my partner and I have actually been discussing this.

I plan to use all of the cash to help fund my next cash-flowing property.The break-even on the closing costs is 5 years when factoring in the mortgage savings.

Typically they need good credit score and proof of cash reserves or income, not looking at 2 year employment as a factor.  

Finishes, layout, updating (or not), general condition and lot quality are just some things that factor into the final value.