I know a sister who married outside the lord and didn't get disfellowshipped, although the elders tried to talk her out of it before she married him. So I don't think they will disfellowship him because of that.
As for writing to disfellowshipped ones, I'm not sure. I think they are more strict regarding having contact with non-family who "left the truth".
As far as I know, the elders' book says they can't disfellowship someone before warning him one or two times.
Anyway, good luck to your friend. How nice to be welcomed by a JC as soon as he got back to the meeting -.-