but I am a little fearful that if #2 kid comes back on the scene things will go badly for our Ds
I think you are right about this and so sorry to hear that you are having problems.
I think it would be good idea to start reading up on the bully policies in your county & state, so if this matter escalates you can be prepared.
or that our Ds will be influenced into being mean also, to gain popularity with this guy
You seem to be are a very proactive involved parent so I would not worry about this one to much.
Hopefully this bully will be influenced by your son!