Ok so I have a different take. This is where your unpredictable behavior will frustrate your STBXH.

Are you puppy buddies who occasionally text, joke and exchange your life experiences or are you the stbxw who has been abused, cheated on etc. and value yourself too much to let him in your life?

If you are going to be the first then let him know. If you are going to be the latter then don’t let him know.