Yes, it's like a cooking hearth that doesn't require a bake bread action, but if your opponents are on the ball they will probably buy at least some of that grain from you. Works well with Market Crier.
Not probably. They WILL. You're basically giving everyone free grain (well not free but they still save an action every time). Who wouldn't wanna get on that gravy train? The fact that they can BLOCK you from getting that extra food is quite ridiculous, which makes the Corn Profiteer the worst card in the game.