OK, thanks.

Now, what are your current questions? I'm guessing they are:
1. How do I remove the scale?
2. Do I need to do anything else?
I'll answer those two, in any case:
1. Lowering your pH to 7.0 and keeping it there will cause your TA to drop, slowly. Low pH and low TA will maximize your chance of removing the stain / scale.
2. I would recommend testing the stain / scale to see what will remove it. You can do so by holding various chemicals against the stain / scale for a couple of minutes. I'd recommend testing in this order:
1. Vitamin C tablets
2. Dichlor or cal hypo granular chlorine.
3. Iron Out powder
4. Sodium bisulfate (pH Down aka dry acid)
You should wear plastic gloves, and put the chemicals in #2 - #4 in a old (but clean) wash rag.