From the sound of this, my bet would be that this is a very small, privately owned business and the employer is also the disrespectful boss. therefore complaining to HR won't help, because there may not be an HR. (Or "HR" may be the chick who's sleeping with the boss.) And of course, no one is going to fire the boss if he owns the company.
I would advise this OP to be more proactive about the situation, in that she begin at once to seek other employment while she is still working there. The boss can be as verbally abusive as he wants to, he sounds like an ugly bully. My sympathies, but come on! He didn't cause this woman to have difficulties and almost lose her baby! She chose to put her perceived fear of what this jerk might say ahead of her and her child's health and well being!
You are putting your heads down and being "good little employees" meekly taking the intimidation he gives out and working harder, struggling to please him so he won't holler at you. But really it's all bluff. If he hits you, call the authorities and immediately press assault charges against him. If he orders you to leave, leave at once and file for unemployment benefits while looking for that new job.
Otherwise, at work, you be polite, professional, and keep your cool, even while he is screaming and threatening. Try laughing at his silly sexist insults and his Donald Duck tantrums. If he fires you, so be it. If you don't get scared and intimidated, he's lost his power.
Keep careful records of what he says, and how he behaves, the dates, times and things he said. This is not so much a record for lawsuit purposes, a lawsuit will very likely not be possible, there's very little chance you can demonstrate this employer has done anything illegal. But then again, it's not a bad idea to keep records of what happens.
Keep in mind, he has no more power over you than you give him. If he asks you (or orders you) to do something unreasonable or impossible, just do the best you can, and don't agonize. An employer can ask you to anything, but if it's not a reasonable request, you can't do any more than your best, can you? If he calls you names, insults you, and you let it get to you, he's been successful. His management technique has worked. He's getting more work out of you with his bullying and insults and threats.
There are no labor laws that require an employer to be polite or fair or to talk nicely to his employees. He has the right to fire you at will for almost any reason. You have the right to quit, any time. Be thinking hard of moving on, because people like this are bad for your inner health and peace. It's not worth it to spend your time worrying with them and associating with them. Be polite, professional, and MOVE ON as soon as you can and leave this bully in the dust.