This is... brilliant. The only slightly sore point for me is the second law; do you just DM that there're always enough people around for magic to work, or do you actually take magic away if the characters go far enough away from civilization? As written, this would seemingly not work well with Spelljammer.
"there must be a group of creatures or objects possessing souls of at least 200 within 500 miles of the target point"
Okay, it doesn't work when your ship crewed by 50 wants to fly away... but just about anywhere in D&D, you'll find 200 critters with an Int of 3 or better within 500 miles pretty easily. Simply because Int 3+ critters are rather common.