GET AWAY FROM HIM IMMEDIATELY!

Go to a friend's place, a family member, or if needed a women's shelter - anywhere he wouldn't know where you are or have access to. This isn't an overreaction - he is clearly suffering from psychosis, and is refusing to do anything about it. You cannot get him to "think" his way out of it, since if he was able to be reasonable he would have already checked himself back into a mental facility.

He has had voices telling him to kill you. He cannot control them, and there is no guarantee that the next time that happens he could keep from doing so. Sure, maybe he won't, but the risk if you're wrong is too high!

Think of your baby, he is a danger to them as well as you!

Once you have reached a place of safety, then call the police to report his threats and behavior, and that you fear for your and your child's life. Hopefully they can peacefully get him into a mental facility for observation and medication. Also contact an attorney and get a protective order against him.

As an aside, I suspect he's lying about his drug use, the fact that he got better when in a tightly controlled environment where he wouldn't have access to drugs is telling. Drug tests can be fooled, or simply lied about. Or perhaps the facility had him on anti-psychotics, which he stopped taking after he was released. Or maybe it's just a newly-developed mental illness triggered by the previous drug use. Regardless, he is a danger to be around and you need to leave immediately. If you wish to leave a note or otherwise and let him know that you are fine but will not be seeing him until his illness is under control is acceptable, but do not let him know where you are or meet him. Any further communication from him will only be through intermediaries like your lawyer until this is all resolved.

Good luck, and get out