I hope your son's recovery is swift. I wish for the best for him and for you. As best you can, inform all the necessary people: medical personnel, lawyers, police, etc personally whatever it is you want them to know. If anyone questions you, say calmly "His father and I are divorced. I think it important that you know this." (whatever the relevant info is) "I want to be informed/notified (whatever fits here) about my son." Tell the medical people about your ex kissing his son on the mouth. That is simply unsanitary. Your son's health comes FIRST before any emotional malfunctioning going on in your ex's ego. Your ex needs to hear it from the medical staff that his slobbering all over his son's mouth can give your son an infection which could be quite harmful.

I empathize quite deeply with your situation. Without going into detail, there was someone in my family who was doing and saying things that were not helpful, and yes, for whatever reason (even reasons that don't make any sense) there are people who make things worse for their own agenda. The sooner you establish that you are the young man's mother and that you expect to be and deserve to be kept in the loop (regardless of anyone else) the better.