Question about Atlass Boss Tree Nodes

Does the difficulty only affect bosses in maps or also other bosses from the Breach, Delerium or Ritual? Since these have their own difficulty modifier, I am unsure if they get buffed too.

After countless of hours I finally got 300 Simulacrium Splitters but then died to the boss, don't want the same to happen again when I try the Ritual one. So, should I remove all points from the Atlas boss tree to be sure?

Also, how do I get the last two boss points for the tree? I am at 8/10 and I did a corrupted + iridiated boss lvl 82 but it didn't drop a book.

My understanding is that the +1 Map Boss nodes do increase the difficulty of the league boss encounters, breach etc and to get points 9-10 for the boss skill tree at the top you need to kill the boss that you face once you have the 3 crisis fragments from the citadel.

U can prolly get 4 more points by corrupting your waystone to 16 or 17 respectively

how can you get a tier 17 waystone?
I ran a Tier 16 boss map that was corrupted and irradiated like I said, I don't know how I can push the enemy level higher than 82.

I haven't done the boss from the citadels yet (still missing one item) but this boss got its own Atlas tree, so I am not sure if he will count against the normal boss tree.