So my son has been married for 2 years,and was served divorce papers yesterday, she is asking for $400 a month alimony, and half of his pension,

Your son needs to get with an experienced attorney to assist him just as quickly as possible. He has 21 days from the date he was served to file his answer to the petition, and possibly file a counterclaim. Alimony is a fact issue, and depends on earning abilities and cost of living. Pensions may be divided, for amounts accrued during the marriage. You really need to get with an experienced family law attorney just as quickly as you can to review the facts of your case and set out a plan to assert your position. Please understand that this site does not allow us to recommend any particular attorney or firm, but I do know what a mess divorce cases can be having handled many disputed matters. Do your on-line research and look for attorneys experienced in high-conflict matters.