Can I sue my former employer for use of my intellectual Property? My position was terminated but I created the position I don''t want them to use it.

Depending on the nature of the IP in question, your employer probably owns it already under the "work for hire" doctrine. Thus, the agreement in question doesn't grant them any rights they don't already have and merely confirms your release of your claims. If you don't want severance pay, you don't have to sign -- but that won't deprive your former employer of the right to continue to use the works of authorship you developed while employed.