Do I have a case?
2 attorney answers
The beneficiary could not be changed lawfully using a power of attorney. You have a case. It is typically the kind of case a lawyer would take on a contingency. The problem you have right now is that the insurance company has apparently paid the money out and getting the money from him could be very difficult. Someone should have placed the insurance company on notice of the issues very quickly so that they would not pay the money out.
I am very sorry to hear of your mother's passing.
You probably do have a case. Your mother's husband is mistaken about his powers as her attorney-in-fact. He was very likely NOT empowered to direct money to himself.
Litigating a case of this nature from start to finish, in my experience, costs in the $15,000 - 25,000 range. That's a guess, knowing nothing more about the matter. It could well be settled with a phone call for only $200 or - on the other end of the cost spectrum - get appealed up to the supreme court and cost near $100,000. Litigation is uncertain.
No attorney-client relationship or privilege is formed by this communication. This answer is to be considered as a general discussion of legal principals and is NOT LEGAL ADVICE. If the asker seeks specific legal advice, he should retain an attorney, who will naturally take the time to consider all aspects of the case and perform any necessary legal research.