Whenever a boss tells you “you're replaceable” they forget the fact that they're just as easily replaceable too.
There is no shortage of minimum wage jobs, you're not special and your threat might as well be empty. Sure, I could be fired on the spot but I could just as easily quit on the spot and find another place to work with no loss or difference. Especially in the current “labor shortage.”
Start paying your employees and treating them better or you will become just as replaceable as you claim they are.