Ugh.. Baby fathers girlfriend

She doesn't let me get ahold of him to see our son who's only 5 months old. She's posted about me on Facebook, called me a bitch, etc. so I've made it clear that she will not be around my son. She used to go through his text messages and message me freaking out. 
ALL I have been trying to do is let him see his son. recently he added me on Facebook and hasn't messaged me or even called (he lost his phone) at all. If he wanted to see his son that bad wouldn't he make a better effort? I'm about to just delete him off Facebook and cut contact. What should I do.