Wow, he is toxic.

I work in a place I call the Kingdom of Dysfunction and that is a familiar tactic. Many times it comes down to that person's insecurity. I don't know the full story, but I would speculate that he feels threatened by you and feels he needs to undermine you and steal your ideas. Sometimes, if the person is not too toxic, a collaborative approach may work. Enlist his help, but document everything and have witnesses if able. Or, if he is too far gone in toxicity, you may just tell him what you have experienced and that you choose not to associate with him any more (if that's possible). Either way, the status quo will not help you and it is unlikely that he will change on his own.

Good luck and I hope it works out for you. I hate that kind of drama.