Custody dispute with BPD ex-husband?

I need un-biased opinions on how to handle my situation! My ex-husband and I have been separated since our son was four months old, so almost two years. I’m a pretty laid-back and passive person, I hate drama and confrontations and so I have about zero enemies. Well, my ex may be considered one. I want to be cordial with him. Hell it would be great if we could be friends, that would a wonderful thing in regards to raising our son. Honestly, it would a lot easier to be on good terms with him and dump my hyperactive kid off with him every now and then but that simply cannot be. He is impossible to please. He cannot be reasoned with. No matter how accommodating I am, no matter how casual I try to keep things, he finds some reason or in some cases makes them up, to fight. He takes the baby for a weekend and forgets to return his jacket when he brings him back. I tell him its cool and just bring next weekend. He never shows up and I send him a text asking if was going to bring the jacket that weekend. What I intended was “will you have a chance to bring it this weekend” but he took it completely wrong and I was treated to a torrent of profanity and misspelled insults. Before I could even begin to process what the hell I said to trigger this, his girlfriend (who I didn’t even know about and who’s home my son was staying at when he was with his dad) begins texting me and calling me names and trying to, as she put it, ‘tell me something about myself’. I was too confused and angry at this point to respond with any sort of rational rebuttal and it melted into an embarrassing yelling match over the phone with his girlfriend. And for the past six months this is how it goes. He’ll lose his mind over some incomprehensible insult he perceives and I respond to him suddenly cussing me out with my own foul words, we don’t talk for a few weeks, he apologizes and ask to see his son and I really want him to have a relationship with his father so I let bygones be bygones and we get along for a few weeks until a new drama arises and the cycle repeats. As sure as the sun rises and sets each day, my ex will be reasonable and ‘normal’ then switch gears to hateful and insane. This isn’t the problem so much because my mother is crazy, I can handle crazy fine. What worries me is he has no common sense or good judgment. For example: While in between engagements (I think he’s in his fifth currently) he was roommates with a married couple and their toddler. He tells me about this arrangement so that I would send our son his way but I know him too well and check things out first. It was pretty easy since the wife, the one who would be watching my two year old son while my ex was working, had every social website she had open to the public and what I learned was she was 19, aspired to be a stripper because she enjoyed dancing, had friends over to drink at least a couple of times a week, often slept until after 1PM and in one recent event had the cops at her house when her husband became enraged during a party after finding her in a locked bedroom with another man and chased her with a knife through their house. Lovely, sounds like a peachy place for young children. My at first ex denies any knowledge of the incident despite the fact that SHE HAS PICTURES OF HIM AT THE PARTY ON THE NIGHT THAT HAPPENED ON HER FACEBOOK. He then scolds me for my accusations and insists they are wonderful people. If those are wonderful people I would hate to meet the terrible ones. So fast forward to the present week. We attend a long overdue child support hearing and upon hearing the payment calculation (which by the way is under $350) he starts pouring out anything he believes will at least delay the judgment. The child may not be his, he shouldn’t have to pay so much for a child he hardly sees, and he wants to just wants to sign over his rights and be done with it. Of course, none of this works and he leaves very disappointed. I want him and my son to have a relationship but I want to know my son is safe when he’s with him. I want to send him off for the weekend and not worry that my ex will take off with him and I never see my baby again. I want to have a decent relationship with my child’s father and work together to raise him. I now keep the baby with me because his mental stability is questionable and I have an obligation to protect my son from anyone I feel poses a threat. I’m at a loss. Do I take the moral highroad and continue my attempts with allowing visits and live with the risks? Or do I lay down the law and tell him he’s had enough chances and he can take me to court? I don’t want be the bad guy in this but I don’t know which option that be. And I did not mean to make this so long, sorry!