You appear to have several questions here that fall into a few different legal areas: termination (employment), discrimination/whistle blowing (employment), non-compete (contract) and waiver (contract and employment). Since this could affect your future, get an Arizona employment attorney right away. He or she can help you sort out your facts and determine your options for what to do next.
I would strongly urge you to contact an employment attorney in Arizona to review the severance agreement before you consider signing it. The agreement you have described appears to contain language that usually appears in many severance agreements. In exchange for payment of a certain number of weeks or months of pay, you agree not to sue the company for any violations of the law, you agree not to compete with your former employer, and not to accept any additional money that you may be entitled to under certain circumstances.
You refer to discrimination occurring in the workplace, which is an issue you should explore with an attorney before you sign any severance agreement. When the discrimination occurred and the details of it will be critical factors for an employment attorney to evaluate whether or not you have a timely claim under Title VII or any other applicable statute.
Also, the non-compete provision should be reviewed to ensure that it is enforceable under Arizona law.
If you believe you may have claims against your former employer and want to ensure that you have a full understanding of the terms in the agreement, you should consult with an attorney.
A "non-compete" clause in Arizona is valid if it is reasonable as to time and distance. If you sign the agreement, you are waiving all claims, including Title VII claims.