do the following...
1) Get ALL of the documents you can get from your personel file.
2) Ask to get your severance in more installments.
3) Ask how long before the company plans to inform the INS to withdraw your H1 or your I 140 ...request for a delay.
4) check with your lawyer and see if he is ok with the company laying off you..and will continue to represent you.
5) Search for a job / job offer on paper that will let you respond to any rfe etc.
6) Make sure you have all your origianls or get copies from your company about your W2, pay records, offer letter, joning letter, all immigration receipts etc.
best of luck.