Hi ez74
I'm so sorry to hear this was your experience. I'm afraid your experience is not unique. Although there are some nice assessors, there are some who are thoroughly unpleasant and, in my view, unprofessional. And you're right, they do often ignore the reliability criteria - though they do have training on it. I'm not sure why the assessor was not allowing you to expand - that is just wrong.
On Thursday you can ring the DWP and ask for a copy of the assessment report - it's a PA4. That will give you an indication of whether or not you are going to get an award. If it's as bad as you think then you may need it to write a Mandatory Reconsideration. (I hope you get a better outcome than you fear).
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems