Fuk me. Weddings and funerals really do bring out the worst in people don't they?
I have a friend whose extended family stopped speaking to her, (3 aunts, 3 uncles, and 7 cousins and their partners - with about 15 kids between them,) after she didn't invite ANY of them to her wedding (5 years ago.) 2 of them got over themselves and started acting normal again after a year or so. But the other 5 (and 2 of the 3 aunts and uncles) have not spoken to her since.
Even her own mother was pretty upset by it. Even though she went to the wedding herself, she still says to my friend that it's HER FAULT all these relatives no longer speak to her, and she 'should apologise to them.' My friend said hell will freeze over first. She said she could not afford to invite all those people, as she and her fiance were paying for the wedding themselves.
In the 5 years, there have been about 8 'do's' within the family; several Christenings, a 40th, a 30th, and two 21st birthday parties, and an engagement party, and she (and her husband,) have been left out of every one. She feels so alienated from her extended family now, and even her mother makes her feel guilty at least once a week! So in the new year, she and her husband are moving 75 miles south to start afresh in a new county, and she says 'fuck 'em all, I don't need this fucking shit!'
You have my sympathy OP. And yeah I would elope if I were you. Your mother is a manipulative control freak.
Your partner didn't ask permission? WTF? It's not 1930! 
If your family are gonna be arseholes, YANBU to elope!