Where are you getting those numbers from? The EPA has agriculture at 10% of US green house gas emissions. A quarter of that (so close to your 2% number) is from methane emissions alone. If you stop farming animals you're also looking at reduced emissions from not using manure and growing less crops since you don't need to make feed.

https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions#agriculture

You don't need a separate machine to read documentation on. You can install gentoo from any live USB. I used mint, for example, so I could have the handbook open at the same time.