Finding a job following dismissal for gross misconduct

I've read this through and a few things spring to mind...
In your favour, you're not a job-hopper ~ you've kept each of the jobs you've had for a decent length of time each. Future employers like that kind of stability. Any decent employer will look at the whole picture and the person standing in front of them. An interviewer's job is to assess the interviewee's potential. Honesty is a huge asset.
If asked about the GM, answer truthfully, then state lesson learned etc. and move on with a positive.
Incidentally as someone previously said some employers slap disciplinaries and warnings more readily than others.
I had worked in various jobs for over 30 years and never even had a verbal warning until 2 years ago. Then myself and my team of 3 each had a rapid succession of verbal and written warnings. I had 2 jobs at the time. Don't tell me I was a different unreliable and dishonest person in my 2nd job, or had become a different person. I knew the truth and it was a kangaroo court. I handed in my notice, worked my notice and jumped ship. I've now got a 2nd job and still work 2 jobs.
Please try and stop beating yourself up. Look to sorting things out with the appeal or move on to pastures new. Not easy in the current climate though but I think you'll be fine once you've found something and can move on from all this.
Good luck x