I read through your updated posts the other day, sorry for not acknowledging. The public are still interested! Thanks for the updates.
Glad the tank is stabilizing. You can always add a half or less a teaspoon of kalk powder to the ATO reservoir. Of course, it needs to be working well too. Some people have even gone as far as using a pH controller, or a controller that has a pH probe, to turn off the ATO if the pH gets too high (which would correlate with high alk and calcium from an overdose).
Acros aren't dead until you finally see algae fill in. I'll take a pic if you're interested of an acro that died up to the axial corallite (the polyp on the end of a branch), and now it is slowly starting to grow back downwards over the algae that moved into its skeleton.
If you want to push down the alkalinity and calcium, you can always add a tiny bit of vinegar. very small quantities, but they'll drop pH, alkalinity, and calcium if added. White vinegar is ideal. It'll also lower your nutrients a bit as well, since it'll release carbon.