Leveling from 80 to 100? [Curious how de-leveling works]

I've been enjoying the end game content. I'm running a pathfinder Ranger. I don't really care about meta's or the most op builds. Not my thing. I just like to have fun.

That being said, what I am curious about is how de-leveling works. I'm at level 80 and from 78 to 80 I experimented in maps to see how clearing fast versus clearing slow would affect things.

All that seemed to change is my xp/hr which ideally the higher xp i earn per hour the faster i level. I was averaging about 40 million/hr.

When I reached level 80 I was at like 3% overall progress. Then I died and it reset me to 0%.

Do I maintain level 80 and the lowest I go is 0% as level 80 or do I get de-leveled to level 79?
Is there a negative xp/hr?

"

Do I maintain level 80 and the lowest I go is 0% as level 80

Yes