Emotionally abusive and oddly naive

I've known this man for most of my life -- since high school, and we are in our late 50's now. We began an intimate relationship in 2001 that ended in 2006 with me wandering away confused and hurt after 4 years of truly bizarre behavior on his part (much of which I documented in writing then, and could have been written today). We reunited in 2018, and things seemed much better for a few months until the same behavior resurfaced.

The name-calling. The Jekyll-and-Hyde mood swings. Erratic and unpredictable decision-making. Abandonment during my most vulnerable time. Unwillingness to plan for, or follow through with, future events. An over-developed sensitivity to perceived criticism. Heightened sensitivity to social embarrassment. Processing information about 10 seconds slower than most. Gaslighting. Blaming. Sexual jealousy (I'm 56 for pete's sake!). Irrational stubbornness. 

Hyper-focused on that which interests him (almost obsessively). Lack of empathy. Inability to sleep through the night—every night. Interrupting and talking over me (and others) constantly. Needing to be in constant motion. None of this made any sense to me. It's as if ... he lives in a completely different world of reason and comprehension. And then, his juvenile responses to and juvenile interpretations of, well, just about everything. As if he got stuck in adolescence or young adulthood in his social and intellectual development.

Could that be? His family (5 children) are all academic over-achievers. Could it be that he intuited from a young age that he was different, and at late adolescence ... just gave up and hunkered down into self-defense? He barely graduated high school (HIM: I never read one book in high school. ME: What? Why? HIM: I couldn't stay interested. But if it's an instruction manual on how to replace a carburetor on a 1968 Triumph, I'll read the entire thing twice.)

I've been wandering through an emotional minefield thinking "What am I missing? What's really going on here? All of this has got to tie together some way, I just can't quite connect the dots."  Because, on the flip side, he is a good man. Generous to a fault. Always willing to help. Master carpenter /craftsman. Kind to animals and children. Brilliant sense of humor. Respectful towards women (except for us with whom he has become romantically involved, apparently).

And then I found this site. And then I began to read, and I've been reading your words and experiences and BAM. DOTS CONNECTING. 

So. Here I am, reaching out to this community. He and I love each other passionately but I can't live with this. We're not on speaking terms at the moment and although he's begged for that to be different, I'm just too hurt by his latest actions. He truly does not understand how damaging his behavior is. 

I highly doubt he was ever diagnosed in elementary school with anything other than "inattentive" and "academic underachievement", certainly not ADHD because it didn't exist as a diagnosis in the 60's or 70's that I'm aware of.

What do I do? This man is my Kryptonite. I'm thinking this is a lost cause and it's killing me.

Thank you in advance for any response,

~ Lee