Contact OSHA anonymously?
They may force him to rectify the situation and/or fine him....
You alerted him of the problem. You offered to fix it. He chose to ignore you (greedy tightwad bastard).
If I were in your shoes, I would have called OSHA first. If you do it now and the guy gets hit with a bunch of summonses, he'll know who "ratted him out" and fire you.
The way a lot of restaurateurs treat their employees is indicative that all they want is to milk the business for all its worth without investing in proper safety protocols for their employees.