I havent been at this for very long, nor am I an expert, but heres what ive known/experienced.
From what I understand, the whole thing about IFing is no spikes in blood sugar during the day. Coffee, with pretty much no calories, if any, should be fine if this is the case. For the same reasons, I believe that any increase from lemon would be negligabile.
I always have coffee in the morning (pre workout) and again after with maybe about a tbsp or so of heavy cream between the two. I also add about 5 grams BCAA's to each. I have seen better results with this than not.
BCAA's are Branched chain amino acids, and have been shown to increase muscle regeneration and building, even when taken alone. However, unlike say a protein shake, it has no calories I blieve, or at least not on any of the packaging, and would allow for working out in a fasted state, but be able to ingest protein at the same time.
Congrats on the rash clearing up. I can understand the wheat, a lot of people are gluten intolerant and dont known it. Though, I dont see anything wrong with dairy. Isnt that considered whole food too?