I have had these same exact issues. I've never had these problems. Then it started with one DC, as time went by, a couple months, I was getting DCed every few minutes.

I know this may a shitty solution for some but I saw one recommendation, which was to do a clean install of not FF but windows itself.

I was having issues on my laptop an with my OCD I wanted to get a clean install anyway. This completely fixed my problem. Since the install about a week ago, I have had FF on 24/7 and not one DC.

Just a thought if anyone wants to keep it in mind. It worked for me so just letting people know.