I know it's the last thing you have been wanting to do, but it's definitely time seek legal council. The longer you let them get away with this shit the more accepted by you it is going to appear. Crucify them if you have to, but the law is the law and it protects every employee from having to deal with these situations. The fact that they haven't at least reprimanded him in an official written form is unthinkable. Don't for even a split second believe that any of this is your fault, or let anyone try and make you believe that. As a supposedly higher evolved specie we have the ability to override saying these comments. Persons such as your co-worker deminish men and the specie as a whole.
Cheers,
Scotsman