The analyses of a text

Amber and Chaos are the only real worlds all of the universe, and the other worlds?Shadows? are all parallel worlds of Amber or Chaos.
Brand, one of Amber's princes colluded with leaders of Chaos to take Amber to himself.
He tried to destroy the Pattern, Amber's other self, but failed.
Now, a princess of Chaos tells Amber's princes the whole story.

"Brand was given what he wanted," she said, "but he was not trusted. It was feared that once he possessed the power to shape the world as he would, he would not stop with ruling over a revised Amber. He would attempt to extend his dominion over Chaos as well. A weakened Amber was what was desired, so that Chaos would be stronger that it now is?the striking of a new balance, giving to us more of shadowlands that lie between our realms. It was realized long ago that the two kingdoms can never be merged, or one destroyed, without also disrupting all the processes that lie in flux between us. Total stasis or complete chaos would be result. Yet, though it was seen what Brand had in mind, our leaders came to terms with him. It was the best opportunity to present itself in ages. It had to be seized. It was felt that Brand could be dealt with, and finally replaced, when the time came."
["The Courts of Chaos" of The Great Book of Amber by Roger Zelazny]
It seems that the leaders of Chaos want to rule two real words and Brand wants to rule the recreated new wold.
I'd like to know why "he possessed" is used, not "he has possessed/ he would have possessed."
And I'd like to know what "stop with ruling over a revised Amber" means.
And I'd like to know if "would be" is omitted before "destroyed."

Thank you in advance for your help.