Although my cat knowledge = zero, I have a feeling you are right about the need to rehome Ti. Even if the whole problem were Miley's attitude, she is the one whom you have to protect and defend. Thankfully, Ti is a cat who would be welcomed into many a home. Maybe he should be an only cat, more probably it is the individual dynamics between him and Miley that are the problem and he would adjust quite well to another home with cats. I wonder if you wouldn't be the better person to rehome him than the breeder?