PIP Mandatory reconsideration advice.

Hi we have recently helped my Brother write his PIP form, and he has received his decision. They have awarded him Standard rate daily living but no mobility after a telephone assessment.
Just to give some background he is 55 years old and has Facioscapulohumeral Muscular Dystrophy which is a progressive muscle wasting disease and severe anxiety. He lives independently in a 1st floor flat in social housing, which he is desperate to move from as he can no longer confidently manage the stairs and they have no lift. He is struggling to move as he is not very computer literate and does not understand the home swap software, the council also have not moved his priority status despite intervention from an OT.
I have looked over the dwp letter and the decision makers report they have completely ignored all of the medical evidence in relation to his Muscular Dystrropy and Anxiety, Consultant letter, OT'S report and Physio report. All of which back up the written submissions on his original PIP form. He said that on the Telephone Assessment he felt pressured to admit to having a hobby and mentioned that he has a motorbike that he sometimes rides.They have based the entire decision of the claim on this.This Motorbike was bought in 2018 he has it ridden 3 times, it has 52 miles on the clock, which is documented in the service history. I also feel his housing situation counted against him.
Sorry for the long post but any advice on how much info to include in a Mandatory reconsideration would be helpful, for example would a copy of the mileage in the motorbike service history count as additional evidence? How much detail regards going shopping ie the necessity as living on own and poor IT/Technology skills mean home shopping difficult.
Many Thanks.

unfortunately I only have the decision makers findings in the award letter, I really wish we had the assessors letter too, but the problem is he received the the letter on the 13th of October, which because he rarely goes out owing to the stairs it sat in his downstairs mailbox for over a week, so I'm worried that if we wait until we have the assessors report we will be out of the 1 month time limit for the mandatory reconsideration.
The advice re content of the reconsideration is outstanding thanks. Can not believe how devious they have become regarding evidence, his OT report states that he came across so anxious on his initial call that they could not actually work out what he was asking for help for, yet the assessor says she found him not to be anxious, which is hilarious as if you were to meet him face to face or via telephone its immediately obvious, as his speech patterns are highly repetitive fast and can seem aggressive with poor concentration and poor contextual recall. He even said himself that the assessor cut him off very abruptly, which I suspect was because of his inability to understand the question sufficiently to get to the point or explain himself, apparently the whole call took close to 2 hours, which I feel was more than he was capable of dealing with mentally as all this happened approximately a week after our Mothers funeral.