fiberglass stain: how much ascorbic acid?

Hello - I have a fiberglass pool that gets brown stains, esp. when I have to use high chlorine levels (as I recently did to get rid of a bad algae problem).

I have used ascorbic acid + a metal remover in the past with success, but I wasn't sure of the correct amount of ascorbic acid to use.

I read somewhere on this site that the "Stain Remover" from Leslie's Swimming Pool Supplies is ascorbic acid. I looked at the site, and they recommend 1lb per 10,000 gal.

BTW, I think that at least part of my staining problem comes from my well water. I will have my water tested, and will investigate ways to handle metal in my well water.

A few questions:
(1) Should I use Leslie's guideline of 1lb per 10,000 gal when using bulk ascorbic acid?

(2) I have purchased Jack's Magic the Blue Stuff for the metal remover. Is this a good one (or do you have any other recommendations)?

(3) Any suggestions on how to mitigate my well water's metal problem? Thoughts I have so far: be sure to add a weekly dose of metal remover; investigate using soft water; filter out the metals from my well water before adding to the pool (somehow - I'm not sure how??)

Thank you,
-Matt