Should I negotiate my severance? - 4 months and counting

The company sent a severance agreement with a release of claims, and I am unsure what to do. I would rather hear the honest version than the polite one. There is a non-disparagement clause. Did anyone negotiate and succeed?

Keep everything in writing and save the confirmation numbers. It saved me later.

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