Oh we all have serious methane moments boys. Just ask our wives. As far as sanitizing the system every time, what ever doesn't kill you will make you stronger. We use bottled water to drink even at home. Remember when you were much younger we drank water straight out of the hose We are still here. As for drinking the water in Mexico...that applies to everywhere we go. Each state or city in the USA and Canada have different water than we are used to at home. Granted a good flush of the system when the camper sits unused for a week or a month can build up some nasty little buggers than need to be flushed. So the 5% rinse is good idea every time you open up the camper. Not sure about the black water tank though. New deposits in there will get rid of any micro nastys there. I would say add some bleach to your water filter (filter removed) and run it through the system with all faucets open until it's clear should do the job. That would end up in you holding tanks to fix them. A rinse of your fresh water holding tank as well. No more beans, chilly or beer will help the methane issue too but that's not going to happen either.
Chuck and Joanne
2014 Flagstaff Super Lite Classic 27RLWS Emerald
2013 Dodge 2500 4x4 Laramie Crew
Equal-i-zer 1200/12,000 4-point WDH