Company is laying off a lot of people but want me to work until 1/1 to get my severance package. If I accept the offer and then take FMLA leave for the last 2 months is my severance in jeopardy?

Had a lot of stressor the last couple of months due to health issues with family. The layoffs were the icing on the cake. Benn there 8 years and want to stay until the end but everyday is a slow drip. I can legit take a stress leave or a leave to care for a family member the last 2 months with FMLA, but will my severance be protected?