The OM exhibits unhealthy stalking behaviors. If I were you, I'd get online and look up the state's sexual predators to see if his name comes up. Cannot be too safe these days.
Inform your parents of this development and warn them of OM's activities. This behavior is concerning especially you have children.
I would advise your S13 to never respond to OM's texts. They do not require a response. Furthermore, you and your family do not need to engage with OM. That's giving your power away.
Jiminy Cricket! I am not liking this one bit at all.