In many cases, you may also find better rates and pricing than big banks. 

I am looking to refi once the rates drop to bring my P&I down and hopefully eliminate the PMI I am paying.

Albeit good deals are harder to find these days given the interest rates.

Small differences in interest rate isn’t wildly important on a lower loan amount.Minimum property value is $75,000 and minimum loan amount is $50,000.

I am trying to be more active and meet like kind real estate minded people.

Rates on a DSCR 1st are pretty low compared to a conventional loan 

I'm proud of the house I created, it's beautiful & I even have a 5.0 rating on Airbnb. 

Realize also you have ongoing costs for each LLC that you set up, Yearly resident agent fees, possibly fees to have your meeting minutes prepared on a yearly basis, Tax preparation fees for each LLC Shell, and You're 1040, etc...

If I buy a small business that includes real estate, it is possible to assume the existing loan (at a lower rate), and finance the additional amount up to asking on a second position mortgage?

You need to define your parameters and identify the types of properties that meet your needs both for living and for an investment.