This is exactly why a lot of folks have been silent since your last "reconnection" attempt. You keep thinking this is about you, what you are doing or not doing. It has nothing to do with you. It is about him. Only him.
You guys have such obvious 3 month cycles. Mine did the exact same thing. I lived it, I know it. It suck$.
Only you can make the decision. Do you keep putting up with this as he spirals, then you threaten, then he "comes" back, life is great, then he disappears. . . rinse, repeat, etc.
I am glad you come here to vent, but those who have followed your story think you deserve way more than this guy is capable of giving, at least in his present state. But ultimately, if you are willing to take what he gives, then that is your decision.
Not sure if you've read HaWho's development on the MLC board, but after years of basement dwelling at a subsistence level her H has suddenly handed her divorce papers and it is making a big push to get out ASAP.
Sometimes waiting around for things to get better works, but usually it doesn't.
I hope you find a good place for you and the kids with whatever you decide. You are one heck of a lady and a hard worker.