@Maplelady I think that at first, your relationship was fine. I feel it might have started him thinking when he moved in and saw what you had and what he COULD have had, if he had acted more wisely with his money. He started thinking and came up with this fantasy, where he could share your wealth, while keeping his. He wants what you have but doesn't want to do the "details", like saving for his own house and saving up to open his own business, so he would have funds for a year or two while it gets off the ground. He saw that you already had a life he liked, part-time work, own your house and you were so much more than generous when he moved in. NVDP wanted that life too, but without the pesky obligations, so he decided, in his little mind, that you should make it possible for him. Even if it meant you lost everything or had less, to him, as long as he gained, that is all that mattered.
YOU did nothing, NOTHING wrong. You are not responsible for not wanting to give all you have away to some dud. You have children and they and you are what is important here. Dud showed his true colors and will not be happy that you weren't willing to give him half of what you have. Don't be surprised if he begins to love-bomb you, wanting to get married because "he can't go on without you". It will be that scenario, or the anger and "I deserve to have the life I want, and you should give it to me, no matter what you want".
Stay strong, be careful and please, please, please, get your locks changed. Also, don't let him into your house to get the rest of his stuff unless you put it all somewhere where he cannot go into your jewelry, purse or get near any valuables. He will feel entitled to take what he wants because, in his mind, you owe him. The fact that he got to have a roof over his head, heat, food and a place for his children for so very little contribution, will not occur to him. He, just like a child, will want to hurt you back. Be wary and prepared.
A lot of posters here, more than I ever thought could/would, have come out to support you. That should show you how much you are valued, even if you haven't met us! We care about you and want you safe, happy and secure.