This is going to take a total of 20,000,000 points to unlock this. The song that I was able to obtain the most points on was Blood On The Dance Floor with a score of 407,074 so I will round down to 400k. That means if you were able to do that EVERY time it would take you 50 times with that song. I would say you will average about 200k a song maybe. That is why it is important to not rage quit while playing through a song since you will end up grinding at the end.
I was level 16 when I finished up everything besides MP so It took a bit of grinding to finish it out.
Play every song on expert even if you are just going for secret freestyle sequences since that nets you the most points.