SSI

Son has applied for ssi and they sent forms to fill out.  How do i convey a lifetime of struggles in one sentence answers.  I understand that he wont get ssi for the autism he'll get it from the bipolar.  The autism is such a part of who he is.  They ask why he doesn't take care of his own checkbook and savings acct.  Of course he doesn't.  He barely goes out of the house and never talks to anyone he doesn't know well.  He's terrible at the computer so thats out.  I'm so frustrated and we have barely started.  
 
What do i write? If they talked to him they would get it but to fill out a bunch of forms that don't convey whats going on is frustrating!