Yes, that is a Pariah cat situation.

I would try:

Prozac (for him)
Feliway
Vanilla on the base of the tails

Defenseable position. Give her a large Tupperware box, with a hole cut in it, that she knows she can run into when they are pursuing her. It is easier to guard one front and not worry about defending from all sides.

I'm sorry that this is happening for you.