Not clear to me. Conditions like "leaky"-ness are not determinate or easily quantified. "How leaky'" sounds pretty nebulous. In what units is leakiness measured? "Diet" is not something you can nail down and start blaming for all your ills, Terry Wahls notwithstanding. It's as leaky as "leakiness".clearly the flora of the intestine determines how leaky it is
Re pollution/water theft/air flight, etc: I think we are all doomed on account of air transport. I bet airplane hours track well with climate temperature, and I think without flight we would not have to worry about climate. But are we willing to give it up? I am reminded of Al Gore's frog in a beaker of water. Before the frog knows it's getting too hot, it's far too late.
Similarly, I went on vacation in Amish/Mennonite territory. If we used horses for many of the things we used internal combustion for, would we have too much methane exhaust?
Modern life is not the cause of MS. Face it, you are sick. You may not get much better. But it's a better choice than no life at all.