I really like the theme behind this game but my girlfriend and I do not enjoy having manipulate a dummy player. Is the dummy player difficult to manage when playing with two or is it even required for the expansion?
Yes, it requires dummy players (two of them). It's somewhat of a pain to deal with the dummy, although not a major problem. The 2P rules as written require each player to give the dummy 1 action per round in addition to 2 random ones, which actually increases the decision space for the game. Here's my variant that plays much closer to the "real" 4P game:
This uses a d8 and 3 extra pieces per dummy to minimize dealing with them but still have a 4P game.