You are doing the same sort of heart-searching I had to do 50 years ago when I married into a lovely Irish family.
My in-laws were so kind and generous in a way my parents could not be. I loved them and they me.
My Mum didn't try to change, even though she almost lost her grand-children with her attitude, because she would never admit she was doing anything wrong.
Dad's loyalty to her meant she had confirmation of her actions, so of course she just got worse.
Like your Mum, mine even wanted me to call my boys by my maiden name, not the typically Irish surname I wanted for me and our sons.
For far too long I went along trying to pacify and please her, feeling horribly guilty and to blame (as she implied I was) for the disputes between us. Now of course I can see where the real blame lay.
It may have continued forever, just getting worse and worse but my Dad died. Mum not only lost her partner of 30 years but her audience and 'enabler'.
My sister was only interested in Mum's bank account, so visited only when she wanted money.
Mum had just one friend and that by default: the wife of Dad's old army buddy. So it wasn't long before they had no reason to visit her either.
I was the only one left.
It took a long, long tim and Mum and I were never chums but I learned to see that making me feel bad was her little power trip (we all have them in one way or another).
That the bigotry was actually fear and she genuinely loved her grandsons.
With no audience to play up to and agree with her, she softened a little - and of course I was all she had.
But I came to see also, that if Dad had not died, she would have continued to rule the roost and be unpleasant until my boys refused to have anything to do with her. Then I would have been blamed for keeping them away.
So I understand your position and my only advice to you Confused2019 is to try and see now that it is not you but her at fault - that you will never, ever do everything right for your Mum, however hard you try.
You can cause yourself so much distress by taking the blame and thinking you can change her by your actions - it will never happen. Accept that and you will be much happier.
Your mother and mine were cut from the same cloth - I only wish I had refused to feel guilty from the outset.
It might have saved me a lot of heartache and tears - the kind you are now going through.