I don't think he’s tired; I think he wants to take on Denji's burden instead. He just wants Denji to be happy, and the only way to do that was to be eaten and free him. As long as Denji is Chainsaw Man, trouble will never let him go
i think pochitas trying to say that, yes denji was happy was certain points, but 1) denji always ultimately chooses hedonism because he will always want more and 2) as long as denji is 'chainsaw man' people will always go after him and destroy whatever happiness he's built. he's trying to free denji in that sense i think, but who knows tbh. next ch will make or break this theory
Wdym pochita ate himself? What reason was there even for it? It was literally “welp, you were happier in squalor, denji and I’ve seen enough. Bye.” It reads more like he’s tired of denji’s shit/tired of being his “heart” that takes over during distress and just wants all the distress to be “over” by reverting Denji back to when he lived in squalor.