We are looking to sponsor what will be the largest deal we’ve done to date.

The sponsor shouldn't get paid out of the CF until the investor gets paid...

Because there is a popular website called Nextdoor that allows realtors to buy or sponsor a zipcode.

Is anyone, especially sponsors who are doing syndications, familiar with D&O insurance & do you have a referral for a good insurance agent/broker who deals with these kinds of business insurance?

A lot of them are sponsored by different vendors like Jet Lending, Noble Mortgage, Quest IRA.

They had great variety and the people who were sponsoring those Meetups were actually doing various local and sometimes large RE investment projects. 

They will know the players (sponsors, lenders, investors) who are active in your type of deal. 

If not, I would recommend finding a partner or sponsor who does.

Too many syndication sponsors are "underwriting to perfection" these days. 

If you're self-employed, a Solo 401k can help to defer a lot of taxes and those assets can be invested into real estate too.It's true that employer-sponsored benefits can be helpful, but a strong income from self-employment is even better, in my opinion.