You should be able to get a restraining order based on his harassment of you in that way. If you have a lawyer representing you in the divorce, let him or her know. If not, you can go to family court and get one. My suggestion is that you print out the comments AND be sure and have a friend who has read it on the actual site (it is possible to "fake" printouts of Facebook pages, so it's important to be able to prove that what you printed out was what was actually posted at the site--otherwise he could delete it and claim it was never actually posted).