Bioplastics are increasingly popular, research is making it better and easier to produce, etc.
I don’t fret over a plastic wrap. For one, if it’s bread in a supermarket, I want it wrapped, I don’t want someone’s sneeze on it.
Plastic for fruits and veggies that you rinse, that’s absurd.
Sure, the grand majority is going to be food waste, but if you threw it all into an incinerator and melted down the ashes there is probably a decent blend of valuable material mixed in with the waste.
Some places do, some don't.
No. Poorly separated wastes in landfill cause non-trivial methane emissions and other VOCs [0]. While leachate _may_ be captured, most of the time methane is definitely not.
[0] - https://www.epa.gov/lmop/basic-information-about-landfill-ga...
Never, because we have virtually unlimited space for landfills, and landfill tech has quietly been improving over the last few centuries, to the point that landfills are cheap, non-polluting, and entirely carbon neutral. Countries with less land mass (Europe et al) prefer incineration (mainly to save space, despite it being significantly worse for the environment and much more expensive (although with the newer energy reclamation efforts this is getting better)).
IMO it's not worth worrying about landfills too much. Household waste makes up about 3% of total landfill waste (when you add commercial/industrial/agricultural) in North America. You and your bun wrapper are truly irrelevant in the grand scheme of things.