Wow that's a crazy side effect to have especially the fever. You said it was bothering you beforehand. Is it possible there is some kind of localized infection or abscess? That just seems a little too coincidentally to have swelling around the gum and a high fever. Perhaps when the amalgam was replaced it allowed infection in?

Perhaps you are just feeling the side effects of ALA? They can be pretty wicked from what I've read. I'm certainly not looking forward to that in the coming months.

If you think it's the ALA causing it, then I would probably stop chelating with it for a few days and start over with a lower dose. It's better to be cautious.