Welcome to MB, fc. I am sorry to hear about these events in your marriage.
Clearly, your marriage never recovered from the previous affairs because your H never admitted to them, and you never began a programme of recovery.
Do you know who the previous women were? Have you any idea whether your H is still in contact with them? For example, if they were work colleagues or neighbours, unless he changed job or you moved house, he could still be in contact with them. It does not help your state of mind not to know the details and not to know whether these threats have ever been removed from your marriage.
I suspect that his recent horrible treatment of you is due to another affair starting. You probably suspect that too, and that is why you have posted on this board.
I don't understand your sentence "I know nothing went on between him and the other women". Could you please explain? You know that there have been EAs and probably a PA in the past.
You need to find evidence of what your H is doing, and that involves snooping on his activities. You need to put spyware on the PC he uses and on his phone. We have a whole forum
here that provides information on how to spy and how to use the equipment.
You seem to be saying that you have no interest in rebuilding your marriage, and that is understandable. It certainly seems as if your H has not taken the "forsaking all others" part of marriage seriously at any time. However, I would still recommend spying to find out what is going on before you make any decisions about leaving. Your six young children would be better off in their intact family - if your H can learn to behave like a husband and father should.
Did you have your first child before you were married? Was there any pressure on both of you to get married? Do you think your H wanted to get married when he did?