I'm with Tripper on this.
We understand it is an "amateur" league but we have some pretty "non-amatuer" drivers, and they will get an insurmountable lead regardless of points system (unless they dnf every other race), so perhaps a system that would differentiate mid-field more could work better for everyone else not in podium.
The 1-point difference system that Tripper proposed seems fitting, that way, as Tripper said, fighting for a position is worth a point instead of having to fight 4 positions for 1-3 points.