Yes, you can collect your debt legally. Under US law, the legal owner of proceeds of life insurance policy is the beneficiary. Therefore it is not possible to divert this benefit to pay the debt of the deceased. In a situation where the dead has left debt in arrears, the creditor can recoup the money by placing liens on property owned.
The exception to this law is this scenario that you are facing. The life insurance company will allow you to collect the debt from annuity because the son shares the debt. Both the son and the father have been tenants in your premises. That means they should jointly bear the obligation. Death of the father will not exempt the son from paying the liability. in joint debts, the creditor is supposed to recover the debt from the surviving partner. Moreover, the son is the only beneficiary of the annuity. That means that no other partner is involved in the annuity that can claim you should not recover the debt of deceased from life insurance policy proceeds. Therefore collect the debt from the annuity of the son because it is legally binding.