Since you're reading the rulebooks and you know the rules better than the DM, just ask to start a new game with someone else as the DM and him as a Player. It sounds like you're not enjoying the current game and that you'd like to give a different campaign a try, just try suggesting to him that maybe you can be DM next week because you thought of a campaign you want to give a try. Maybe he'll be a better player than he is a DM.
I hope this has been helpful, I know it's not always easy to confront someone like that, but maybe if you present it as something you've been wanting to try for a while, and he'd get a chance to be a character.
I've had plenty of DMs who run a character in the game, and I've seen characters that were just part of the party, and I've seen characters that were important plot devices. We had one DM Character who was with our group for WEEKS and he was the leader of our small group, we relied on him to be the most trustworthy character and only after something like a month of playing and knowing this character we learned that he was actually an evil shapeshifter who was trying to kill us! It was CRAZY! And the DM didn't play him as evil, he just played him as a part of the party who had his own goals separate from our own. It just turned out that one of those goals was to lead us to his boss and have us get killed.
In another game the DM created a sidekick to one of our heroes who was just a kid. She was our companion and didn't do a lot of fighting, but it was our job to keep her safe. Which made her death really, really hard for our group. She was used by the bad guys as a human sacrifice in an attempt to summon a monster, and it worked and it took control of her body and none of us could bring ourselves to shoot her because she was "ours". She wasn't just a monster, she was "our sidekick". But she was also a horrible monster, and we let her go. I still wonder what the DM had planned for her, and if she still exists somewhere in the background of that world.
Being the DM isn't just running the game, it's very common for the DM to have a character and use that character sometimes as a cattle prod to move the story forward and sometimes just have the character be part of the group.
I hope this has been helpful. I know you don't really want to be a DM, but it's a totally different experience and totally worth trying out at least once.