Last year, I purchased a SFH under market at 7.65% interest rate and did some rehab to up the value.

Most on-market deals will likely not fit your investment criteria unless you allocate a substantial downpayment, often at least 30%-35%, or negotiate a price reduction that fits your requirements.Furthermore, while this is not the case for all metro ATL markets, my team and I typically see that a solid portion of the small multifamily space is comprised/orientated in neighborhoods of other small multifamily properties.

We own SFHs in Columbia SC and like that market.

For all methods you would want to find a market that has strong employment rates, strong income rates for the market, and is a growing or an established market. 

STR seems to have better tax benefits (in the right market) but is it worth it at a distance ???

Delevan is a market where you will have to look at surrounding markets like Janesville, Elkhorn, and Darien to get your comps and rent information. 

Plus, you already know the market, which gives you an edge.

How do I access a portion of that equity to fund the purchase of 1-2 more MFR properties in more affordable markets like OH, IN, MI, PA, TN, or AL?

If you haven't checked the market for homes with "inlaw suites" or whatever your market equivalent is that can be a way to get it done as well. 

Fairmont is a good little market!