Employment Law Questions? Ask an Employment Lawyer.
Hello and thank you for entrusting me to assist you. I am sorry to hear about what's going on with your boss.
If you have already reported this to HR, there most likely is no "next step" as the conduct you are describing does not violate any law and is viewed as a purely "internal" matter. In general, the law imposes very few restrictions on interactions between employees and their supervisors. The law does not require supervisors to treat their employees respectfully ***** ***** refrain from using foul language (only verbal attacks which relate to legally protected traits such as race or religion are illegal). The law also does not prevent targeting or even terminating an employee based on personal dislike or the perception that they are "threatening" the supervisor's position by applying for it. This is company politics. Company politics are often dirty and unpleasant, but courts simply will not intervene in company politics.
So really all you can do is continue to bring the inappropriate conduct of your supervisor to the attention of HR and your supervisor's boss. Most employers will not tolerate the sort of behavior you describe, but the law does not require them to take action. So, your only power here is the power of persuasion. And if that does not work, you would not typically have any further recourse.
I hope that you find this information helpful and am genuinely sorry if it is not what you were hoping to hear. Please do not hesitate to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further.
If you do not require any further assistance, please be so kind as to provide a positive rating of my service so that I may receive credit for assisting you. Very best wishes moving forward.