I don't really have any advice, but just wanted to let you know you are not the only one in the situation.
I'm in the midst of it - grievance was turned down, and I submitted IT papers. I also put in a subject access request, which I would urge anyone in this type of situation to do. They are supposed to provide the information in 20 working days, but mine took over 5 months and my employer still didn't provide all of it, and withheld other stuff. What I did discover was that the day after I made a report of wrongdoing about a colleague, my line manager initiated the first of 2 covert investigations into me.
It's really tough, especially when it seems everyone is telling you that no, you are imagining it, or that the behaviour was entirely reasonable. Legal appear to be especially vicious, but I suppose it is their job to defend to the hilt, and it's not personal, even though it feels like it.
I've been off sick since I found out about the covert investigations - I've been having panic attacks and sleeplessness. Awful emotional eating, and it's so difficult to switch off the replay of events swirling around my head. GP has given me beta blockers & diazepam.
What helped me is that I went to the oversight body for my workplace and discussed the issue. They were supportive. They viewed the investigation in response to the whistleblowing as corruption and have said if it isn't adequately investigated they will call themselves in. I also found that preparing a visual timeline which analysed all of the records, e-mails etc was useful, not only to show others, but also in an attempt to remove the information from my head and onto paper.
I wish I could be more helpful - try to focus on Christmas as a distraction. Have you looked into any meditation type things to help with the anxiety? I keep meaning to, but haven't yet.