This is how we had it last year:
FGA : -0.45
The current scoring system you have set up is way out of whack. Inflates scorers, doesn't punish poor FG% or poor FT%.
Apart from Crazy's suggestion of adding a differential for Offensive Rebounds vs Defensive, I don't think we should stray too far from this scoring system. It's built that way for a reason because it's meant to be balanced based on overall performance.
I suggest we stick with the scoring above and perhaps give 1.75 or 2 for an Offensive Rebound.
Fouls should not give minus points either.
Let me show you why your current system doesn't work. Let's take a very basic statline, one guy goes for 20 pts another goes for a 10pt 10reb double double.
In your system:
10/10 guy - 50 pts
20pt guy - 40 pts
In the normal system:
10/10 guy - 22.75 pts
20 pt guy - 15.5 pts
As you can see the % difference between the two performances is vastly reduced with your system, meaning simply scoring points is a faaaaaar more valuable attribute in this scoring system you have proposed.