Ultimately it is your choice, but keep in mind that changing your name might upset and hurt the feelings of your mother and step-father. It would be very easy for them to take it wrong. You might accidently open up some old wounds that might exist betwen your mother and father, and it doesn't sound like you have as close of a relationship with your father, need to be careful not to hurt your mother.
As for the difficulty to pronounce the name and going into the film industry,This might not be the best example, but, remember that they had said that Arnold Schwarzenegger was told that he would have to change his name if he ever wanted to go into acting because nobody would cast him because of the difficulty of spelling and pronouncing his name. If you are doing this for the film industry part, something you might consider doing is using your middle name if you have one as your last name. This is done sometimes, or another last name in your family.
Just my advice, that may or may not be good.