I agree, much of the issue is the desire for anonymity and mistrust of anyone with an offer that sounds "too good to be true."

Yes;  at times is may seem as though, despite all our efforts, we may experience various negative events or emotions in our lives;  despair, anxiety, fear, apathy, mistrust, anger, or whatever.  

And I get you are mistrusting.

So again, why all the mistrust?   

All-in-all, if you mistrust this individual you should stay away from the deal. 

Real Estate Investing can wear and tear people down and turn them into cold mistrusting individuals who assume the worst.

Admittedly, I’m a mistrustful person, but my first thought was that I’m a nobody to him and the house was a good deal which he probably passed on to a preferred client.

It sounds like your relationship is based on mistrust or poor communication, or both. 

Also, how would you handle the other co-owners - most of whom are very mistrustful and would prefer to have them all gathered together and have offered and agreed to the same sales price and not to make agreements with me one-by-one.

I closed on that property, and I'm actually working with the same realtor again on another place so I don't have any mistrust in her now.