Questionable Employer Ethics and Compensation Questions

Hi, I've been working at a company for over 10 years and have noticed several areas of questionable discrimination, although I don't know whether that term can be applied legally to these situations:
1. I am told I cannot work from home, although other employees are allow to do so. I have never received warnings or concerns regarding my work ethics, nor have I ever been provided a direct reason why I cannot work remotely. There is no reason for me to be in the office all the time based upon my position, and there are others who are never in the office with similar backgrounds and higher positions. It costs me almost $14/day to commute.
2. There are several individuals who have been hired without announcement from the outside, when there were qualified individuals within (some of which are also never in the office).
3. There are 2 different health plans provided to employees, one is better than the other but only the executives and religious employees are entitled to it.
4. Company has a history of actual discrimination from employees who were previously terminated and filed grievances.
5. People have been 'laid off' only to have others replace them in the same position. This in my view is illegal.
6. I've worked a lot of unpaid overtime but not been compensated.

I have some issues to boss but am ignored, which has over time I feel jeopardized my own advancement and there is possibility I will be 'laid off'.

I plan to leave the company and secure another position but I would like some legal advice as to how I can actively pursue any of issues stated and be compensated for some benefits I feel I am entitled, including severance (I don't have a severance contract).

Thanks