I've been trying to understand Tezuka for almost two years now. I think, finally, I'm as close as I'm going to get, at least from the canon now available.

I think, like Aja says below, it's about courage. To me, it seems like stupidity for him to keep playing, but that's clearly not the take-away. If Tezuka doesn't do his best until the end, he's going to let so many people down, including himself.