I don't have any suggestions, as I'm still waiting to make my first GF batch (I finally transferred my non-gf out of my primary, and I'll probably be busy every night this week, so hopefully saturday!) but I'm wondering about your buckwheat. Did you malt it, then roast, or did you soak it an then roast? Are you doing this as a partial mash, or just steeping? What did you do to yield a 'crystal'? How dark did you roast the buckwheat?
I'm very interested in how this turns out, as buckwheat and sorghum are both ingredients I can get locally, and at reasonable prices.