what'd famine mean when he said sam had no limit...
(feasting on demon blood that is)...
and what exactly did sammy do to famine there at the end...
I didn't catch the meaning of that stomach ache he gave famine...
It looks like Famine had been feasting on souls, and I would assume that demons have juicier ones then we normal humans have. So that Sam literally ripped all the demons out famine. Which I would assume either ripped him apart, or drained the power keeping him going (they did say Lucifer let Demons to care and feed him, to make him ready).
As for Sam, I would assume (though I could easily be wrong) that Sam no matter how much he drinks, would ever get to the point where it would kill him (including the withdrawal) as Lucifer wouldn't want him dead (especially before he was raised and able to bring him back.
I mean seriously imagine Sam feasting before Dean broke a single seal, and going into withdrawals that killed him long before Lucifer was raised. We have seen no evidence that a Demon (on its own) could resurrect him. A crossroad could, but we don't see them use their power except when making a deal with a human, they say their are rules, perhaps they couldn't just bring him back without a human making that deal.