Differentiating between CFS and Effects of Meds

I read something really interesting about 'Reasonable adjustment' and I wish I had requested that my husband's PIP assessment had been recorded. Instead we have been told to submit more medical informtion and we are collecting that at present.
Trying to Homeschool my son who has Autism and fill in two PIPs and my husband's ESA has proved challenging and I didn't pick up this information before the at home face to face took place. I wish I had put more about the way CFS affects his ability to answer questions and he just froze at the intereview. It was clear he could not even process what was being asked of him.

I am trying to locate the paperwork from years and years back from the DWP which sites me as my husband's appointee but I can only find my son's. Now that I am filling in my husband's ESA I wonder if it may be a good idea to include a letter signed by my husband stating that I am to act as his Appointee. That was we won't have to have the stupid conversation with the Assessor (who had no record of me as Appointee) again if we have an ESA face to face next.

Any advice would be so appreciated.