6-figure salary workers generally get severance pay
Not necessarily. My company doesn't do any severance, and that's true for many (most?) companies in my state. The only people getting severance are those who work for a company based in California or Washington or something where that's enforced at the state level, and the company just made it standard across everyone.
they run hospitals, school districts, multiple floors of office buildings
Some do, but many don't. That said, if you're making six-figures and are reasonably competent w/ money (not a given), you'll have a cushion of investments if there's some kind of mass layoff or something.
They are not necessarily the bourgeoisie, that's mostly the top-end execs making 7-figs or high 6-figs w/ generous options. There are a ton of people making 6-figs who fit into the worker class that merely get a taste of some of the things the bourgeoisie take for granted.
Six figs these days is middle to upper-middle class. Upper class starts at the mid-to-upper six-figs.