Thanks to all for working hard for the OP's client. Those of us who deal with disabled children are often left on our own to find out how to best help our kids... We have run into "professionals" who have had less knowledge than they should, and often must rely on the wider community to get suggestions and answers.
"all the help they can get": In most localities, there are disability "rights" organizations which can sometimes represent disabled people, and always can steer towards quality advice. In our case, we recently went to a free seminar where a former SSA employee gave some great advice in plain language. While your client likely has been dealing with the process for some time, even those of us who have, should always be listening for changes, new interpretations, and for things we have missed. If I knew then what I know now... can be costly (as I again recently found out). I did not realize there was an auto qualifier for utility discount if a household person is receiving benefits, which for us, will be more than 20%! I knew about the plan, but they buried the auto qualifier deep, and only plainly show the income qualifiers. For SSI recipients, CA recently joined the majority in allows recipients to qualify for food benefits... which the person who shared to me about the utility discount had missed. And, since my daughter's benefits will eventually be based on my SS amount, I need to be sure not to file before my benefit hers will be calculated on is at it's max, and I severely regret some of the choices I made regarding income in my young adult life, zero and low SS wage years are painful, should I not make it to max benefit age for her.