No, the SH will not harm the stone. Delco sight has changed to powerwash.com. Just call them if you want to order Jason. You may be overthinking this a bit, but that's the way you are and that's ok. Just Take the advice of these professionals and go get that job. CAll me if you need too.
+3 on ox acid. Works great on concrete. I sometimes use it on large planters that have small cracks and little stains from the minerals seeping out. The ladies love it. Also for grills, ornamental art work, metal chairs or anything that leaves rust stains. Sometimes it will take a coule of shots but fades with time. Also brightens fences and decks.
if your going to use OX, let it dwell. Vertical surfaces are more difficult, cause the product won't stay there long enough. Another Phenem product is OneRestore from Eachochem. They will also give you tons of tech support! Love them guys @ EachioChem!