SuccotashOk5676's journey

I recently ended my employment after receiving a Final Written Warning and being placed on a Performance Improvement Plan (PIP). The company offered me 4 weeks of severance, totaling $10.3k, but I decided to counter and ask for 4 months instead. I feel justified in my request because I was the top contributor on the main codebase, with 960 commits and over 222k lines added, while the next highest contributor had only about 393 commits. I also completed a significant refactoring project that reduced an 8k line class by 71%. During my time there, I consistently worked long hours, often exceeding 14 hours a day, including providing offshore support in the evenings. I managed to keep up with my responsibilities even while dealing with a serious family medical situation, attending calls from the hospital and rarely taking leave. Additionally, I had raised concerns about the complexity of the codebase well before my PIP. I worked remotely from Texas for a California-based company, and I already have another full-time job lined up. I'm wondering how realistic it is to negotiate the severance from 4 weeks to 2-3 months or even higher. Do my significant contributions and the concerns I raised give me leverage in this situation? Should I consider bringing in an employment lawyer at this stage, or is it better to negotiate on my own? I'm also curious if anyone has tactics that worked for them in similar performance-based exits.