I'm sure - in his mind - nothing is ever his fault.

You have believed that somehow his thinking would straighten out. It won't. No matter how good to him you could ever be, his opinion of you would always be based on whether or not you granted his last request. Say "no" and you go to the crap list, no matter how many nice things you've done. The trap is that, when you say yes, he just loves you to pieces, and can seem like a good guy for awhile.