Thanks! Gypsum is calcium sulfite, used to harden your water and often appears in british-style ales. It also lowers mash pH, so I always use either that or Mash 5.4, but not both.
I haven't seen lcasanova's brown ale, but I'll check it out.
Why so many grains? Well at this point I'm still doing a lot of experimenting, plus I steal my wife partially-used GF grains from the pantry
(just kidding I ask 1st)
If I wasn't experimenting so much, I probably settle on about 50% base malt, and I'd likely use quinoa. Then I'd use about 20% crystal, probably quinoa again. I'd keep the oats. For this recipe I think the roasted amaranth and buckwheat were very important to darken it up and add depth to the flavor profile. Something toasted and nutty is also always a good idea for browns. But the more gains the better (quantity-wise), so your brown ale doesn't taste "citrussy", courtesy of the Sorghum.