Vegetables grown in shit, garbage, and pesticides are fine as long as the levels of harmful residues are low enough by the time they reach people's mouths. Not appealing, but also not that "dystopian"
Using manure and compost as fertilizer is likely as old as agriculture (though i disagree using pesticides is fine). What did you mean?
Plenty of substances bio accumulate, and being less than careful with animal waste as fertilizer causes outbreaks and disease.
Ha yes of course, this is obvious to anyone in the field but always a good idea to repeat. For example, do not use human feces as fertilizer for food you'll eat (at least not directly).
Ack, yeah it's one of those 'well duh', until people who have no idea blindly copy the idea and then plague, or prions, or arsenic poisoning, or whatever.