You've got plenty left. Pause>Stats, the bottom tab (I forget the label) shows you overall progress, including story mission progress /69.Just wondering how many missions are there?
Mission I just did:
Just did the port heist, where you can either go rob the ship or use the submarine and rob the bomb thing underwater,
How much do I have left? I hope it's a lot.

I may have to replay this game again once I know what I'm doing with the stock market. I am seriously poor at the moment lol