How to keep mom from running my wedding by her "illnesses"?

Sounds to me like your mom is using her "illnesses" to manipulate the event to her own (selfish) preferences. RE: the groom's brother: Tell her that it is as important to you to have the brother there as it is to have her there. Suggest that she take some kind of tranquilizer & deal with it. Her "phobia" is prejudice & unreasonable.