I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today. I have been a CA licensed attorney for more than 3 decades, and I handle real estate law and landlord tenant law.
Unfortunately, under CA law, a promise is not enforceable in court and any agreement for the lease of real property, to be valid for longer than one year, must be in writing. The fact that the owner willed the property to charity suggests that his promise that you could stay in the rental was intended to mean only while he owned the property. Under the circumstances, the only way that you can continue to stay in the rental is if the person who buys it also wants to rent it out and they allow you to stay on.
A "pocket listing" is simply a property for sale that has not been listed in the MLS yet and means little in your situation. And it is quite possible that the executor already has the Realtor chosen, but no, there is no such thing where a Realtor gets hush money to not list a property. Any seller, or executor, can direct the Realtor not to place the listing in the MLS. There would be no reason to pay a Realtor not to place the listing in the MLS.
I understand that you may be disappointed by the Answer you received, as it was not particularly favorable to your situation. Had I been able to provide an Answer which might have given you a successful legal outcome, it would have been my pleasure to do so.
If you have additional questions, you may of course reply back to me and I will be happy to continue to assist you further until your questions have been answered to your satisfaction.
Would you please take a moment to positively rate my service to you based on the understanding of the law I provided by clicking on the rating stars---three stars or more. It is that easy. That is the way I am compensated for having helped you.
Thank you in advance. I wish you the best in your future,