Without knowing the complete financial picture here, it is hard to say conclusively, but it does sound as though the VA did not factor something in.
To get the VA to reconsider infromation regarding the award, simply do a VA form 21-4138 - Statement in Support of Claim providing them with any additional information to reconsider the claim.
Has the amount of monthly care expenses changed since you made the original applicaiton?
Take a look here on the forums under Tips and Resources, and then look at determining Countable Income. Do that formula to help you know exactly where he stands at the end of the month financially. If he is at zero or negative, then yes, you need to get with the VA to get things straight.