It appears that in your reference to your dad's military exposure to toxins, you are asking about eligibility for service connected disability benefits. In that case what your mom is entitled to receive depends on what exact benefits your dad filed for prior to his death. The botXXXXX XXXXXne is if he did not file for specific VA benefits, any entitlement to those benefits (not filed for) died with him. Richard v. West 161 F3d 719 (1995)

I must assume that is the problem she is running into with the VA at this time.

To determine what benefits may be available on his record, she will need to obtain a complete up to date copy of his VA file to review exactly what impairments he did or did not file for with the VA. She does not want to waste her time simply guessing as to what was on record with the VA. Submit a VA form 3288 to obtain that VA claims file copy. Look through the file to see what if any benefits he filed for with the VA prior to death.

Terms and Conditions: By your continuing in this conversation with me, or by your clicking “Accept”, you are expressly agreeing to all of the following: (1) our communication is for non-legal non-representative consultation purposes only; (2) you are not consulting me in my professional capacity as an attorney; (3) you do not seek to establish an attorney-client relationship with me, nor do I with you; (4) you will not rely on anything I say and you will obtain appropriate legal counsel via a traditional/office consultation with an attorney licensed to practice in the jurisdiction where your legal issue arises concerning the matters discussed. You declare that any payment made by you is not consideration for contract, nor offered for any services, legal or otherwise, rendered by me on your behalf. If you do not agree with these terms and conditions, then you must advise me immediately.