There are actually very few laws in the workplace regarding how the employer is required to treat employees verbally. If they physically assault you or threaten you, press charges. Call the police.
As far as verbal insults, if you have told the employer respectfully and politely, when he says things like this, that you do not appreciate him calling you names, and requested that he please address you respectfully, and you have documented these incidents and your efforts to ask others to get him to stop, talked to the other owners and to HR, and you feel that you have exhausted all reasonable alternatives to dealing with this problem, then the NEXT time he jumps in and yells at you, calls you names, etc. then you might quit your job, as soon as it happens. Don't hit him, scream at him, curse back or call HIM any abusive names. Just quit, right when in happens again that next time.
And in that circumstance, you may be able to get approved for unemployment insurance while you are looking for another job. It won't be much money, it wouldn't be approved for many weeks from the time you filed it, and it will end abruptly after six months, whether you've found another job or not. But it's pretty much your only alternative if you quit.
What you do not want to do is go quit the job now because sometimes in the past he has used abusive demeaning language to you. This is called the "my boss slapped me last February" scenario. If it wasn't bad enough for you to quit at the time, then you've accepted the work condition that he calls you names sometimes. If you continued to work there after the behavior occurred, and you did not try to make it stop through other means (exhausted all reasonable alternatives to quitting) then they say you must've been okay with it. But now that you've tried to get others to deal with it, the next time it happens, you may quit and be approvable for unemployment. But it's not a sure thing. If you quit now based on his past behavior, very much not likely.
I'd suggest looking for another job before you quit, while you are still working for them, then you won't be without income and you can leave quickly when you do find a better place to go.
I am not at all sure there would be any type of EEOC grievance for you even if there were enough employees there at the company. Unless they can show that the employer was treating you this way solely because of your race or sex or any of the applicable issues, and was creating a pervasive pattern of discrimination against you because of this, it'd be hard to show that his generalized abusive language was in violation of the EEOC guidelines and protections. There's no law against using abusive language to employees in general. Are you the only woman, minority, etc. who works there? Does he treat the other people who work for him this way?
