I found after a tank year my tank went through an evolution and became much more stable and predictable. Then I didn't ever lose any SPS frags I added and 38 of them grew into colonies.I was able to maintain pretty much of the coralline I had from the reboot (pretty much the back wall). But the SPS might be challenged because my parameters wander a bit
So sounds like you are on a good path with knowledge. Maybe the tank just needs a few more months of stability.