Oh my goodness -
you have not read Rule's book!
"The Stranger Beside Me" is almost exclusively devoted to why Bundy became a monster. Their relationship was only a small part of it. A few excerpts:
Chapter 49 - devoted to the origins of antisocial personality, and parallels events from Ted Bundy's life from the very beginning that made him this way.
1. He was raised believing his biological mother was his sister. When he found out the truth, he hated his mother for lying to him. He never knew who his biological father was.
2. Raging ambivalence towards mother: she treated him like he was special, unique, and destined to achieve wealth and greatness. While her ministrations fed his ego, he felt very insecure about living up to her expectations. Believed all of his life that he was destined for greatness, and yet never quite achieved it. Resented his mother for placing an inordinate amount of pressure on him. Roots of his hatred of women in general can be found in his relationship with his mother.
3. He also hated her for marrying someone of limited financial and social means – Johnny Bundy (who adopted him). He considered Bundy an inadequate role model of manhood who did not adequately support the family. Bundy resented their low socio-economic status and was very, very insecure about it. Resented his mother even more, because if she could not find success and stability with her husband, it placed an even greater burden on Ted to be successful.
4. Rule also goes in to the origins of why almost every one of his victims had long dark beautiful hair - because the first woman who rejected him fit this profile. Bundy above all could not take rejection.
5. The book also quotes extensively from the psychiatrists who examined him and the conclusions they drew about the origins of his behaviors. Rule extensively delved into Bundy's background and again drew parallels from Bundy's early life that contributed to his deviant behavior:
Psychopaths usually become that way because of events that happened to them before the age of five. In an addendum in the book from 1989, Rule reveals that Ted's grandfather Sam Cowell, whom Ted for many years thought was his biological father, and who he apparently idolized, was a tyrannical and often sadistic man. When his daughter Louise gave birth to Ted (illegitimately), she was forced to leave him in a foster home for several months. Abandoned babies often have trouble bonding. And when Louise finally retrieved him from the foster home, there was a lot of shame and rage and anger about the disgrace she had brought on the family. They concocted a story that her father and mother adopted the little boy, so Louise could never fully act as a loving, nurturing mother towards Ted, less the secret get out. His grandfather was not very nurturing, and his grandmother was very ill – some hint that she was profoundly depressed and bedridden for most of his childhood.
The book is full of the type details the OP claimed to be seeking. They are well researched and substantiated.