Nice tank!
I skimmed through your thread and for coralline to grow:
1. You have to have good cal and alk levels.
2. You need to have coralline to seed the tank, I simply took a hermit crab shell and scraped it off in the water column.
3. Coralline did not make a appearance in my tank until the 7 month mark.
I wish I still had some Stomatella snails in my tank, unfortunately my scarlet skunk ate every last one, maybe 200-300 all within a 3 month period.