i agree it doesnt sound like typical adhd behaviour, maybe he was crying out for attention seeing your son was getting it by seeing nurse , he might of felt excluded
he might be pushing you to see how far you would go in public, maybe just a sugestion that when you need to go to places were you attention needs to be placed on one boy ask for help get a friend to go or somebody else

also if hes playing his father up it might be again playing one parent agains the other as children tend to do this just to see if somethings going to happen