That plot twist was inspired by a fan of BB who had inoperable brain cancer.
The cast of BB visited him and asked him how he’d like to see it end.
I think the “It made me feel alive” line was a direct result of the boy’s input.
They offered to let him see the final ep script but the kid said no, I’ll watch it.
He didn’t make it.
Walt was dying and the whole meth mess made him feel alive, in the face of it.
you already got him pretty much admitting that in season two talking about it with the new guy in chemo in the lockerroom/dressing room.