Hi Larry, glad you decided to keep the 3913 and to try and adapt to it. I feel that the first DA shot is the hardest to master, but after doing so the SA shot becomes much easier, as you have already become used to the grip and built up some muscle memory. Not to mention that it is just plain easier to dry-fire practice in DA with the 3913, simply hold in place and keep pulling the trigger.
Like 18DAI mentioned, hundreds of dry-fires will really help with this pistol. The Hogue grip sleeves have been mentioned for a better grip and that's not a bad idea either, I personally like to use a strip of traction or grip tape on the back of the grips.
I own many TDA S&W 3rd Gens, but have no problem transitioning to DA Kahrs, the original Ruger LC9, or revolvers - more of an automatic adjustment with each, though I mainly practice with TDA guns . Everyone is different, but for me it seemed to expand my muscle memory rather than replace one with the other.
If you swap in the lighter Wolff mainspring, I would recommend just going down 1lb in weight, and making sure that your firing pin channel is nice and clean. I have read that one of the reasons for the stronger factory mainspring is to ensure that the firing pin makes it through any blockages with a dirty firing pin channel with enough force to set off the round. Removing the safety body and firing pin would be the best way to get things clean, but a pipe cleaner through the breach face side of the firing pin hole will work good too.
Good luck Larry, and I hope you are able to find some common ground with your 3913!