I like the 2 points per sack but could agree that dropping three and outs and / or making them 2 points would work. 4th down stops could be 2 points instead of current levels although they feel exceptional in the real game.
Defensive yards seem ok to me, it's unlikely that teams will achieve <100 regularly. Points scored though definitely, 40 is excessive, I'd start that at 20. 20, 15, 10, 8, 4, 2, 1 perhaps