That depends on if there are orders in place to prevent it. The bexar county website does not seem to provide any, but check by calling the court. If there are standing orders, that means certain behavior is not allowed and normally one of those listed is changing beneficiaries on policies like life insurance.
If there are no orders in place to prevent him from changing beneficiaries, then yes, he can. You can petition the court to put those orders in place, but it may not be worth your time and effort. Unless the final orders require him to keep the wife as beneficiary, he will be able to change it in the future.
Disclaimer: This answer is intended for educational and informational purposes only and should not be construed as legal advice or forming any attorney-client relationship.