I read the whole post and he doesn't give me the impression of being at piece. If you're truly at piece you wouldn't be writing such a long and bitter post to begin with. He pretends he doesn't care for money, but all the examples where he felt he's not being treated fairly revolve around money. And he clearly still sees himself as one of the original Minecraft creators while he's not.
At peace? The fact that he wrote this long post shows that he is not at peace. And it's not like it was just a vent piece that he didn't expect to get attention, he posted a link to it on /r/minecraft.
