He actually believes what he's saying, even when it's not true

I know, this is an endless topic... my husband who has mild ADHD really believes everything he says, even when it's completely false.

Example: We have been arguing about a renovation that needs to be done - since last spring - it's now November. He will not commit to doing it, yet he won't allow me to go ahead, even though I want to and can pay for it, because he wants control over it? He doesn't really want to do it? Not sure. Last Tuesday I confronted him again, and he said he would get back to me in 3 days with his answer. Well, he went away camping, and 3 days were well past, so I told my husband I am calling a contractor, he is free to participate, but we're going ahead. This is a reno that is really much needed, in my own workspace, and if we don't do it soon, there might be health issues because of mold.

Suddenly he tells me that the very next day, after that 'wait-3-day conversation', he had told me that he agreed to do the job himself, with all kinds of details about how and when etc!!!  We. never. had.that. conversation. I tried to get him to tell me which day, which time of day, what room were we in, when he told me all this stuff. He just gets angrier and walks out.

He yells at me, telling ME I am only using this topic as an excuse to yell and be mad!!! Hell, I would have been DELIGHTED if he'd actually offered to do the work. Why the heck would I want an excuse to be mad? On top of that, he blames me for all the defects in the previous work that was done on the house and property because I'm the one who hired the workers. You would not believe the stuff I'm responsible for, every leak, every tiniest problem, 1/4 inch off square in a corner... sometimes I think I might be responsible for WWI, the Big Bang, world famine, and maybe even global warming. For sure, global warming. He makes me feel like s---. But on the other hand, he will never actually commit to BEGINNING anything, so naturally I am always perfect for blaming.

But he believes it all! It's kind of insane. At times I think I will have to just blow my head off to feel better. Different versions of this story happen all the time. He tells outright lies, but to him, they are truth.

Can someone please help me think this through and find a peaceful space. In most things he is a kind, gentle man. No one would believe me if I told them this stuff.