Your character’s transformation isn’t drastic enough. You need a more seriously flawed protagonist from the get-go— someone with oodles of room to grow. Don’t be timid with him. Even likeable, “normal” people are messed up and make decisions that blow. Make him muck things up quite steadily, even as he tries to fix whatever needs fixing. Only when he’s in dire straights will he be ready for the epiphany or idea that propels him to success and a new awareness about himself or the world. Test it: When he reaches The End, extract him from that last scene and drop him back onto Page 1. He should handle himself so well that you wouldn’t even have a story if this were the guy to really start it.