Workplace Rant....What to do?? Kinda Long...Sorry

Sounds like the supervisor needs a review from the owner.
He threatened you because of his ineffectiveness and may
be hiding something you or the company is unaware of.
An internal audit may be in order to discover where the
true problems lie.
Might send an anonymous letter to the owner detailing
problems as observed by the peons and see how that is received.