The newest development between the Mouser and the Catzilla brothers is not good; I think was Billy who put a bloody scratch on the nose of our gray overlord. Minor, really, but it doesn't show things improving between the boys and the new arrival.
It may be time to look for a new home for the Mouser. He will not go to a shelter. We'd keep the Mouser here under supervised quarantine first, and it has yet to be even near that state of affairs. But it is a quality of life issue for all concerned, human and feline.