Roosters don't usually do that much in terms of protecting the flock. If you're concerned about predators, fencing in a large run would be a lot more effective. Obviously not as fun for the girls, but effective.
I have roosters too, but I only keep the gentlemen. There are plenty of good roosters who need a new home out there. I bet if you look around (craigslist, Facebook, etc), you could find one to replace him who has a better temperament.
And please don't be too hard on yourself. There is only so much people can do to try to settle down the boys who have misplaced aggression. If he's sucking your joy from having chickens, he's not worth it.