OP you can show they discriminated against you and you MUST claim for it.
You have anxiety which I don't think you realise meets the definition of disability, especially as you have had it for over a year at least. You also mention having made them aware of this but they don't seem to have made any adjustments to help you do your job or to their investigation / disciplinary process to make the experience less anxiety inducing for you.
You're a victim of harassment becuase your boss said "its only anxiety" in an email or something you saw. Harassment is negative behaviour towards someone with a protecte characteristic (which includes disability)
You've experienced victimisation as he's saying you're a liar, criticising your disability and also because they are penalising you for recording your sessions - I used to be a union rep, and I'm disabled, I am sure I have come across tribunal cases where the recordings were permissable as evidence because they evidenced harassment/victimisation/whatever discrimination it was. You could say that due to your anxiety, you record meetings to minimise your anxiety and ensure you fully understand what is happening. They should therefore allow that as an adjsutment.
You've experienced a failure to make reasonable adjustments to help you manage your anxiety at work and also to the process to minimise the anxiety to yourself. As an adjustment they could have kept you better informed during their investigation etc, undertaken it quicker and also allowed you to record.
So three areas of discrimination at least. I don't know if you still have a union rep and/or a lawyer but you definitely need to get onto them. Also try the formal grievance website.