Severance agreement arrived, need a second opinion after 13 years as a machine operator

I was offered 13 weeks of severance after 13 years as a machine operator, and I have a few days to sign. It has been weighing on me all week. There is a non-disparagement clause. Did anyone negotiate and succeed?

I asked for two more weeks and a neutral reference. They agreed to the reference and added a week.

Thanks for writing this out. I went through something close to it 3 months ago, and it got easier once I kept a simple log of every call and form.