If the ability has damage divided as it was put onto the stack, the division can't be changed, although the targets receiving that damage still can
Madness doesn't give you another chance to cast it later
The first part of that sentence is the most damning part, unfortunately, and has gotten her on Gavin Verheys own list of mistakes
Be prepared to activate Elixir every game and win by decking with Malboro ETBs
Marcy: This card got a lot of play in the Bloomburrow pre-release and preview content that came out, and for good reason: it makes Lizard typal Rakdos work VERY well, allowing you to filter your deck very, very easily and find exactly what you need
If you're playing a deck that isn't too loaded with monsters, you won't really get the best of what it has to offer