I know this may not seem possible, and probably not the answer you were looking for, but it would be worth partnering with another active investor, bringing in a passive investor(s), or even waiting until you have enough capital to deploy into the right deal. 

Whereas the majority of the existing clients have stayed with you, but the whale client is with the ex-partner leads me to believe that if this heads to any type of judicial setting that no damages would be awarded.

The major point to that statement is anything else but cash in your hand is speculation.

Active real estate investors who can't get comfortable not being in the driver's seat, people who just don't like real estate as an investment, those who can't get comfortable with the risks, those who just don't understand syndicate investments, those who have heard bad things about this type of investing from others, and people who have invested in syndicates and experienced bad results.

However, I have also studied this and have seen that the majority of those who lost was because of themselves.

Even including modest appreciation and equity pay down, the ROI is between 7% and 12% for a non passive holding (not good for an active holding)I can easily afford this level of negative, but do I want to?

Most serious and qualified tenants are searching on the major 3rd party platforms you mentioned + realtor.com, redfin, and a few others.Apartments.com & homes.com are owned by the same company and may offer some additional marketing options.Another strategy to consider here is social media - video marketing.

Regarding your second question, are you asking if those activities help meet the IRS material participation tests or qualify you as a real estate professional?

This property I previously modeled is now active for $1.789M, if you check the model I was at $1.75M.

Red Stick has an active FB group