Feed Question

I've searched through the old posts in this forum and also around online looking to better understand how to figure out the protein percentages in custom feeds. I've seen statements to use the crude protein percentage and other statements that say that you should use the digestible protein percentage (which is a lower amount than the crude protein). I'm not sure which I should use. Is the protein of the hay supposed to be included? Sometimes I see nothing about the hay and other times I see things about how alfalfa uses a feed mix that is more towards 12% protein and grass hays use mixes that are more toward 16% for the feed (for does in milk). Does that mean feeding grass hay and alfalfa pellets has you wanting to use 12% protein feed mixes?

I want to do custom feed so that I don't use corn or soy which it seems every pellet uses. The only one I've seemed to find around here that doesn't have it is a feed that predominantly uses peanuts and I've heard bad things about using them specifically for goats. Even most custom feed mixes I've seen use corn and/soy or things like calf-manna which has both. I called a co-op that's not far from me that I saw offers custom feed mixing and I asked them about making something and they asked why I wouldn't just use their feed mix... When I said that I was looking for a feed that had no corn or soy the guy just sat in silence on the phone for what felt like several minutes, I thought we had gotten disconnected but I think he was just judging my comment for whatever reason.