Being bipolar does not excuse some of that behavior. You need to tell him (hopefully when he is stable) that his behavior is unacceptable and that there will be consequences if he continues.
You should tell him that if he threatens to physically harm you, or physically injures you, you will call the police.
You should tell him that if he is verbally abusive toward you, you are going to take the kids and leave the room, and he is not to follow you, or maybe that you will take the kids or spend a night in a hotel, or that he has to leave the house for an hour.
You should strongly encourage him to get help. If you still want to continue the relationship, give him a time limit. Tell him that you want him to get better, that you will help him get better, but that if he is not getting better in say, six months, you are leaving.
I doubt people like that will ever be easy to live with, but if they are not following a plan managed by a psychiatrist, then the probability of them getting better on their own is too low to even consider.
If he is going through an episode, he may not want to listen. He might need to fall hard, wind up in handcuffs or worse before he realizes that he needs help. All you can really do is help him the best you can and remove yourself and your children from the situation if and when it gets to the point that you cannot handle it (especially if he is not being treated).
You also have to be sure that you follow through on any consequences you promise. It may be hard to call the police, or leave him alone, but you will ultimately be helping yourself and hopefully him.
Also, it does sound like it could be bipolar disorder. Lots of times psychiatrists miss the other "poll" and they diagnose the condition as unipolar depression. Anti-depressants run the risk of triggering mania or mixed states in bipolar individuals.