Shouldn't it be ", Sacrifice a creature: You may cast ~ from your graveyard without paying its mana cost until end of turn."? It's simpler to make the cost for the ability and make the creature free.

I'm not sure why you would want to cast the creature as opposed to put it directly into play. Sorcery speed issues, perhaps? The fact that your opponent can counter it is considered a control factor? "Whenever you cast a green creature" style cards?

Mmm.... if you've got a sacrifice on the board, can you cast this from graveyard again and again and again? That's somewhat different from the usual "Comes back to life" stuff, if intentional.

Sadly not: once you cast it from the graveyard, the game loses track of the object it was in the graveyard, as it's become an entirely new object on the stack or the battlefield.