I've not read the whole thread but I will.
My last name has six letters. My ex has eleven.
I work as a nurse and was not going to sign charts with his name. I kept my name. At church I was known as Mrs. B as his name was also difficult to pronounce.
I've been divorced for a while. We are civil at family events. Our children have his name. He is their father.
My son has a daughter out of wedlock. We weren't sure if he was the father and so she had her mother's name. I had a DNA test done and he is definitely the father. However he is a single parent and she was in daycare while he worked. When she started writing her name I told him to tell them to teach her his last name. The daycare staff's reaction was that would be so difficult for her. His reply was, "I did it, she can too." My feeling was if she started with her mother's last name, 6 letters, she would be confused when we tried to switch it. She if 5 and can write it and spell it correctly.
I also chose not to have children until we had been married for about 5 years.
You have to do what is best for you at the time.