I am one of those “I only have one mother” people. My MIL, no matter how close I am with her is NOT my mother. There are certain titles that IMHO belong only to certain people. Mommy/Daddy is one of them.
In addition, I knew my MIL for a few years before my husband and I got engaged. So I always called her by her name…it seemed unnatural to me to change that. My SIL just got engaged and her fiance is also planning to call my in-laws by their names.
Oomis, I just want to let you know that what you did for your MIL is amazing!