Anecdotal experience (Long-time Land Cruiser owner in Western Norway where the SOP at first snow is to salt the heck out of it) suggests that Toyotas do rust like mad; I work hard all year keeping my Land Cruisers (a 1981 BJ42 and a 1998 KZJ95) reasonably rust-free. I have to treat them to lanolin twice a winter season.

Yes. There was a decade or so of production truck frames for Tacoma and Tundra trucks where Toyota paid to replace the frames due to rust. It was supposedly a supplier problem.

Yes -- just search classified ads in northern states for Toyota trucks with new frames.