Sevarance

I was terminated from employment after 2 years because I was "not working out."
I have received 2 performance increases.
Totaling $10000.00 (annually)
I reported to the VP of Operations, who implied that he couldn't wait to get the extra person in my department, where as we could implement and develope procedures where needed, and continue to develope the companies growth as a team. I was a hands on manager and worked many hours in order to fulfill my duties.

In being terminated, I was given a severance package, signed by the owner, and have taken it home. It releases the company of any and all liabilities, past present or future. (I have yet to sign the package, and there was no implied deadline on it.) rcvd 9/24/04.

My problem is that an employee that reported to me, made an insinuated threat of bodily harm to me. (My boss made me hire her back after being let go for refusing a drug test after an injury, and stating she would not pass it because she used drugs.) After the threat I reported it to my boss and he said, he'd talk to her. I also wrote up the situation and reported it to the HR Coordinator. My boss was furious at me for reporting it. He and HR investigated it, she admitted it, then they agreed we would "evaluate" things for 2 weeks.
She later started making crank phone calls to my home. I reported this to my boss and the CFO, and he told me that this was between me and her, and literally blew me off.
I guess my question is two-fold.
With the original copy in hand, and signed by the Owner, can I ammend the contract to better protect my interest, and it be binding?

With the stipulations of diparagement and defamatory statements, can I not make that binding for "Employer Parties" as well?


(I am not certain about paying for consultation)