Pip Appeal and sending information ahead of the tribunal

I've received my PIP appeal bundle, and I'm getting a little overwhelmed and anxious about the whole thing.

I receive the standard rate of PIP mobility, but I'm arguing that I should receive the enhanced rate as I'm in constant pain. Every step is painful, but stopping to rest only exacerbates the pain.

I resist using a wheelchair or mobility scooter, as I know that my fitness levels would plummet further and my pain would increase through lack of movement.

Unfortunately, I have very little supporting evidence as my spinal surgery was in 1988 and I was discharged from the pain management system in 1994 as there was nothing else they could do for me. I don't see a consultant regularly as my spinal surgery was for a congenital condition, and they've done as much as they can for me.

I really struggle to talk about my condition without bursting into tears, and I'm worried I'm just going to be a blubbering mess on the day.

I read about the legal precedent CPIP/665/2016

A significant new legal judgment holds that while someone may ‘push through pain’ in order to continue walking this does not mean that they are walking to an “acceptable standard” for Personal Independence Payment (PIP) purposes.
The new judgment means that consideration should not only be given to whether a disabled claimant can reliably walk up to 20 metres or 50 metres in total.
In addition, consideration should also be given to whether they are walking through pain before reaching 20 metres or 50 metres.

Would there be any benefit to me writing a letter ahead of my tribunal quoting this in the hope that it won't actually get to the hearing stage? Or should I just let it run its course?