Perhaps go to the back and explain to a FA.
"I think a PAX may be being disturbed by another PAX but I am uncertain. She appears uncomfortable with the adjacent male and I do not want to intrude."
Edit: just re-read this. Oh yea. Would ask him how long he's going to pull that. I think common courtesy (which probably doesn't exist here) would be to request a seat change with PAX behind. Alternatives would be to out-annoy him?