TBH, marriage would have been the perfect time to drop the first name you don't use.
It's pretty common in some parts of the UK to have a first name and a middle name and to use the the middle name as your given name. You can specify on most forms these days how you'd prefer to be known.
From reading your posts, I get the impression your parents made what they thought was a harmless joke rather than anything cruel, but being the butt of that joke, you spent the first 18 years of your life being exhausted by it, and perhaps at the point when you were legally allowed to change it, gave up the fight?
I think it's true that parents can have a far bigger impact on us than they realise. It's annoying to change a name, but not impossible, and whilst I would have changed it by now in your shoes, I can see how you're too full of resentment to do so.
Do you at least like the middle name that you use as your given name? Did they get that right?
If it's along the lines of you were born Miss Ann Sally Teak and you're now Mrs Ann Sally Jones, I'd just call myself Sally Jones on everything, or perhaps A Sally Jones. You're entitled to use whichever of your two names you prefer - legally, they both belong to you.
But with the surname gone, does the first name really sound so bad now? I know you don't identify with it, but something like Ann Jones is fairly inoffensive. Can you try to detach the negative feelings of Ann Teak? Then if someone calls you Ann, it's not your name, but it's not upsetting, just mildly annoying.
People get called the wrong name all the time and brush it off - just today, someone asked me to sign for a parcel and gave me the wrong name. Along the lines of, 'delivery for Tyler' rather than 'delivery for Taylor'. I know my name is Miss Taylor not Miss Tyler, so I shrugged it off.
I get called the same wrong name all the time, but I don't have any negative associations with Miss Taylor, so it doesn't bother me. You need to find a way of distancing yourself from that previous you who was so wound up at school.