Settlement Offer

Several months ago I wrote my STBX a letter asking to stop the litigation. In it I gave a dollar amount and some terms if litigation would stop.

In that letter I wrote "This is not a legal document or agreement, nor is it a formal offer. It is simply a plea to do what is best for everyone involved. It is a plea to stop all the litigation and attorney costs, which neither side can afford. "

Is this legally binding? If so, do I need to do a formal withdrawal of this offer or something similar.

In the context of marital litigation settlement negotiations are just that, negotiations. They are not binding and are not admissible in court.