A few brief comments on Sauron's part:
This one is probably much easier! A simple AABB scheme, and longer lines to work with. You got the translation down cold!
How dare you to enter my domain without my leave?
In my shadow where all birds and beasts bow down to me?
You have donned the garments of a minstrel wanderer
But your blood carries the scent of Western usurper!
[here again you have the rhythm shift, carRIES, U-surper. Maybe "reveals" instead of "carries"?]
Peace across all Arda has been shattered in our time
Steel on steel is ever ringing, blood flows out like wine.
Brother turns on brother since you came to Hither Shore
A curse has come on Arda, and its name is Fëanor!
["A" sticks out but I think it's doable, wouldn't change it]
Aaah! So malevolent!