Well by your header and letter for this topic I think you are looking for some genuine input, so without further adieu.
I worked in restaurants for about a decade, and I would be the goto guy just like you, I worked on the premise that it HAD to be accomplished no matter what kind of self-sacrifice had to occur. And I was only an official manager a couple of times. But still I showed up I did what had to be done because I have pride!
This is what I learned: The reason I was the goto guy was people knew I would say yes and take advantage of that, not always but enough. When I really looked at it for myself it was all based on ego, even though I was overworked, under appreciated, I wore that shit like a badge.
"Yeah thats right I'm working fro open to close. Some people needed shifts covered no-body would do it so I stepped up to the plate."
That is just about one step above being EMO I could puke. I found that I didn't have HAVE to do jack except exactly what my job description said. Calling replacements and covering shifts that are lacking is a MANAGERS responsibility
From the way it came across your boss is over relying on you, and you allow it. If you don't want to take on his duties also then don't. If communication is lacking then go to his boss. It sounds as if your boss took on to many roles also, and if he cannot accomplish all of it then he should step down from one or the other.
Good Luck, and no guns!!!