The idea for keeping the pH down is to try to avoid further staining.
Lowering pH has the direct effect of lowering alkalinity - this is good for your pool but not the goal right now.
Your high alkalinity will cause your pH to trend up due to carbon dioxide outgassing.
Keep the pH low to prevent additional staining until you can start applying the HEDP metal sequestrant.
Ben will advise you how to proceed once metal sequestrant is in hand.

Frustrating - yes - but you are waiting for the HEDP and keeping the pH low is the best you can do until then.

You'll be fine - really. No need to panic.