I have friends and worked with people in wheel chairs. In my initial ignorance, I was surprised at the range of impact the wheelchair has on different people’s lives.If you get PIP this carries on past retirement age. If you are of retirement age you have to apply for AA (Attendance Allowance nothing to do with drinking!). People are staggered as besides ling term Type I I have had a leg amputated and spend most of my waking day in a wheelchair! I have been unsuccessful so far and found most (so called) charities next to useless!
Subsequently, I have learned not to make assumptions based upon “just” having a wheelchair.
That said, I am sorry that your disabilities impact your life and yet you are struggling for them to be recognised as impacting your life sufficiently for PIP.