Does your employer have more than 100 employees and more than 50 were affected by this layoff? If so, you may be provided protections under the WARN act requiring 60 days notice for layoffs.

If not, there's no federal requirement for severance pay or advance notice of layoff.

If you had $3M in cash to invest right now, would you use it to buy this stock?

You should probably sell off most or all of it and diversify.

How much is remaining in the 401k and what is your current taxable income?

If the regular annual distributions are already pushing into the top tax bracket, it might not matter that you're pulling out 200k at once.