I share your difficulty with the 3913 in the ways that you have though I have not pursued resolve to the extent you have. I have changed out the grip to the Hogue grips but have not enjoyed any resolve.

I shoot 124 gr in this pistol and my groups are insufferably low and left.

I do think a trigger job would help though I now subscribe to the "not every pistol works for everyone" school. I'm keeping the 3913 because it's a classic and it's cool to me.

The last thing that I can offer in terms of information is that I mainly shoot Sigs (P229 Extreme, P229 SAS, M11 A-1, and P239) and I'm dead on with those leaving me to think that it's the pistol more than the shooter.

I may try 147 gr in the 3913 to experiment.