Creative ways to deal with crazy boss?

I am a grad student with about 4 years down and 1 left on my degree.

My adviser has slowly gotten worse over the years. He was always a little flaky and difficult, but he has what seems like full-blown, extreme ADHD and probably a personality disorder. He doesn’t understand anything that’s going on in the lab and it’s impossible to get him to help with anything.

We have all found ways to kind of “manage” his crazy, but lately he has found a new thing to do: be a complete, raging asshole.

I met with him earlier this week and asked if I should register for a conference that we all go to every year. He said yes, and he is happy to pay for it. I told him thank you, and I would also like to apply for some travel awards to help defray the cost, as long as he was willing to write letters of support for me, which every award requires.

He said of course, and went on a long tangent about golf (“never putt short on a birdie!”) I remember this entire conversation very distinctly.

Yesterday, I emailed him the contact information and deadline for the first of the travel awards. He replied, “You need to ask if I am willing to do this. You did not do that.”

This is infuriating, because:
1. The actual amount of work he needs to do is almost nothing. The letter is already written (he asked me to write it for him for a different award), so all he needs to do is send the email.
2. The travel award saves him money; I don’t get anything out of it except a line on my CV.
3. Why on earth would he discourage his advisee from applying for awards?
4. I DID ASK HIM AND HE SAID YES.

I emailed him and apologized, saying I thought we talked about it when we had the golf conversation, thinking it would jog his memory. No luck—he just emailed and said fine, I’ll write the letter, but you did NOT ask me.

What the fucking fuck do I do about this guy?