re. creativity of the DMC. It all depends on the skills of the DMC and what you want him to do. If you want him to be the start of all your attacks, looking for killer balls from deep and he has the skills to do it (eg Pirlo or Alonso type player) then really you want him to have quite high creativity (high normal I'd try first). If you want him to destroy the opposition and play simple passes to better players, then you'd want him on quite low creativity (something beneath normal) as you don't want to risk him trying silly passes and them not coming off (eg Makelelelelele, Essien, Mascherano type players).
If you want to be a bit different, you can actually have your deep lying midfielder as your playmaker, while your other midfielder is the ball winner. This works very well when the ball winning midfielder has skills to be a threat to goal as well as a big engine (eg Keane or Gerrard type player) and the deep lying midfielder is capable of stupendously accurate long range passing or needs a lot of space in order to do his job (Neil Webb looked a million dollars for Nottingham Forest in this role).
There are a few ways to run a 4-4-2 even with a flat midfield 4
re. passing - don't go so short that your player in possession does not have options. He should have 3 simple options at all times in the middle third of the pitch - forwards, backwards and to at least one side. Your passing should vary depending on what you are trying to do with the match. If you're defending, then short passing at the back is asking for trouble - but short passing up front will keep the ball up at the oppositions' end. If you're attacking, then short passing up front may not get the ball out wide quickly enough to stretch the defence - whereas a more direct style of play will do. But you don't want to be hoofing the ball forward to be dealt with easily by the opposition's defence so you'd want your players at the back to play a shorter passing game so that they find your creative midfielders who can pick out the killer balls.