Not to mention sky-high drama factor.

Key Questions:Would it be more financially prudent to sell the rental property and pay off a chunk of my high-interest primary mortgage (7.375%), and use the remainder for a fix and flip?

With 7 properties I would highly suggest getting a PM software to help you.

The other factor that's relevant for me is that my husband is a high end W-2 wage earner and we could greatly benefit from the potential tax benefits of actively managing the property. 

I highly recommend you create an "Animal Addendum" which is a set of rules for any animal, whether it's a pet or service animal.

BiggerPockets also has a calculator to analyze deals, and I highly recommend you start this as soon as possible, even if you are not ready to buy.

Understanding your top priorities can help in determining whether Stessa, Baselane, or another tool might best fit your needs.If you're comfortable with apartments.co for rent collection but want higher yields on your cash (this is me reading between the lines) you could have the transfers go into a high yield business account like BlueVine 1.5% interest or something like CapitalOne 3.9%.

Keep in mind, it would be in your best interest to go for as high as 4 units on each purchase to maximize your door count. 

Highly recommend starting close to you so you can get eyes on the property if you do decide to purchase a true rental. 

I definitely think in my area, many of the good opportunities I could qualify for with my income would have pretty high rehab needs before they're rentable, so it's good to hear where you would start out instead.