I'll bet the live show guarantee is divided equally, because that's still a hell of alot of dough. Stevie and Lindsey get their songwriter royalties, and Lindsey gets producer royalties, so they're making considerably more in the long run.
I could be wrong(
), but it IS Mick and John's band. I know S&L could refuse to tour unless they got a bigger share, but I doubt that's the case.