Need help with ubers boss difficulty explanation

Hi,

I am a bit confused from the following:

I put 6/8 on the Breachlord tree, and my breach boss area is level 82. Does this mean that I am at the last difficulty because the zone is level 82? Or if I put the last 2 points on the tree, the difficulty still goes up? Because based on my experience the zone was level82 again when I went 8/8 on the tree.

Also, is loot affected by difficulty? More specifically, if my zone is lvl82, is loot affected if more difficulty is stacked on the tree?

If someone could explain, I would really appreciate it. Thank you.