I am worried that my x is screwing my 9 year old son up. He is a terrible example of anything.
He doesn't work or have any ambition in life to do anything that doesn't involve driving fancy cars or buying ridiculously expensive clothes. He is a terrible example of how to treat women. And now he's knocked up his girlfriend of 3 months. My son is obsessed with fancy cars much like his father and he is becoming a bit of a spoiled brat.
How can I explain to my son that the way his dad lives is not the norm and certainly someone I do not want my son to become?
I think what you are telling me is that you are fearful of him becoming a dead-beat like his dad.
But lets look at this logically...your son is only 9. Your son will be influenced by both you and your x, both in positive ways and negative ways. So, that means he is more than likely trying things on to see what fits. In other words, he isn't making life decisions that cannot be undone; and quite frankly, I don't think he is doing much more than finding commonalities between he and his dad.
Remember that your child has different parents than your x, different experiences, and different genetics. Those three things alone will direct your son on a different path than your x. He also has you, who understands the importance of integrity (words and actions aligning), and how to build character, and the difference between working hard and hardly working!
Have you introduced the concept of good choices and bad choices? It is a bad choice to only play and not to work, or go to school, as it pertains to your child. Explain why this is a bad choice (because working and/or going to school teaches self confidence, teaches us to overcome obstacles, teaches us to get along with others, communication, etc. Conversely, ask your child what would be good choices. Ask your child what if mom decided not to work...what would they do for food, without money, how would your child play sports.
Then, I think it's ok to explain to your child that sometimes moms and dads make bad choices. That is true after all. However, we hope moms and dads make more good choices than bad. I don't think you should point out all the bad choices the other parent makes, but introduce the idea to your child that moms and dads do make mistakes and are not perfect. And again, begin asking questions. Do you know some bad/good choices mom has made? What are some bad/good choices dad has made?
Those questions alone will open the dialogue to get your child thinking independantly and forming his own decisions.