does my employer have the right to

Your question is very complex and there are numerous issues to address. First off employment without any specific agreement to the contrary is at will. This means both parties can choose the end the relationship for almost any reason. With that being said the first thing I would suggest is that you review the terms of your employment contract. Check to see if it speaks to any of the issues presented. If so than you can simply apply those terms. If not my answer speaks to the general and I would advise you consult a local employment lawyer to review further with more specific facts to see if you do in fact have a valid cause of action.

First with regard to mileage reimbursement, without written contracts stating it will be paid in general an employer is not required to pay for such costs.

Second with regard to cursing at the staff, although very unprofessional it is not a crime. However you can speak more specifically with a local attorney to determine if the type of language and what is said violates any other laws such as harassment etc.

As for docking pay this is where the issue arises. Your contract should state when and why pay would be docked. if the employer chooses to do so arbitrarily he may be violating state laws with regard to employment. I don't have the specifics but please review the specifics with a local attorney or even re-post here with some examples. I would say it may very well be a violation and something you should look to pursue. Good luck