I thought I read a FC recommendation of 2-3 always.
That must've been some miscommunication somewhere. Since your water hasn't had a chance to receive the dissolved stabilizer, the bleach will be more strong without any buffer, so a smaller 2-3 goal is good on day one. After that though, always refer to the Chlorine/CYA Chart (link in my sig) to balance the FC and CYA together. While your CYA is 40 now, it may change later in the season, so when it does, always go to that chart to ensure the FC matches your current CYA.
As for a SLAM, we'll be happy to guide you through that as well. You'll want to ensure there is no algae in the water before you receive the Magic Jacks, so the SLAM would be the first order of business. Gee Bob, now that you say that, I need to modify my instructions above - I'm sorry.

Let's do it this way....
A SLAM requires a pH between 7.2-7.4. I'd go for 7.2 if I were you based on other factors. It will be fine. Next, do you have the sock(s) soaking for a CYA goal of 40 already? If so, that's fine. Then you can increase your FC to "16" tomorrow morning. Usually I'd say start now, but I don't want to aggravate the metal residue in your plaster if at all possible. So by tomorrow the stabilizer should all be dissolved (squeeze frequently if needed), make sure the pH is at about 7.2, then push the FC to "16" and keep it there all day tomorrow and throughout the evening as best as you can.
Since you just did a 100% drain, your SLAM should go quickly as I suspect any residual algae would be in the plumbing or filter. If you haven't done so already, you might want to rinse that filter tomorrow as well, but continue to maintain the FC at 16. Tomorrow evening, try an overnight (OCLT) test as explained on the TFP
Pool School - Perform the Overnight FC Loss Test (OCLT) page. Take your last FC test about bedtime, then take another FC test in the morning before the sun hits the water. Since you are doing a SLAM, the pump will already be on continually mixing the water (low speed is fine) which is great. You might get lucky and pass the OCLT (Thursday morning) by not losing anymore than 1 ppm of FC overnight. If you pass, the SLAM is over and you can let the FC fall naturally by the AZ sun down to the normal range.
That should do it for now Bob. If you have any questions, just holler.