As soon as you play a card, it is discarded. There is no limbo area where cards float between the time they are used and the end of the turn. As Steven W said above, however, "B" will make the game a bit harder, but not break the game.
Overall sounds good. I can definitely live with A.
I wouldn't call it a limbo though. The question would be: Are the cards played and discarded one at a time? Or, are they played and discarded at the same time? No limbo involved.