I think you are making the right decission Wayne !!!

Getting all your kitties spayed sounds perfect ; after a while they will settle down again , and they will be much less agressive !!
As to your poor Princess , I know it will hurt like hell , but you are right : she would be much happier as an only indoor-cat !! Be sure to find her a good home with people who are prepared to love Princess with all their hart and cuddle her as much as they can ..! I wish you very much success with your search !!

Let us know how it goes !!