Don’t worry about the copper. You probably heard that on a BD board from someone pontificating about how to make, use, and store BD their way. If you don’t agree with them, then you don’t know what you are talking about. But, if you dig a little deeper none of the “experts” are heating with BD. My experience, and it is only my experience, is that copper lines are just fine. Been running BD100 or close to it for 2 years in my workshop. I use copper lines gasp and even more scary…I use unwashed BD GASP I migrated to this site because no one claims to be an expert. Instead everyone shares what works and doesn’t work for them. For instance, this year I have had a few failed starts because of cold BD. You are correct that this group is primarily focused on WVO and SVO applications. But Jesse and the others don’t mind a few of us BD people hanging around too.
I know for my area, your inside tank has to be at least 2 feet from any fuel burning appliance. But check for your area, local codes always overrules provincial (state) codes. For fuel lines I believe stainless steel may be your answer, but I’m not 100% sure on this. Expensive, and difficult to work with!! Lines and SS flare fittings are available.