Is it illegal for someone to post how much money I received on Facebook?

You may want to consider hiring a lawyer to send a Cease-and-Desist letter.  While a cease-and-desist letter has little legal impact, the lawyer's letterhead gets the recipient’s attention.   This is a relatively inexpensive way to put the person on notice that you are not going to let these actions continue and that you are serious about pursuing your legal remedies.  It also tells the person that they could get in legal hot water which will cost them a lot of legal fees if nothing else.  This will often convince them to stop their evil ways.   You will want to discuss your situation with a lawyer in more detail. Many lawyers offer a free phone consultation.