Interesting analysis. I'd agree, except that we just learned that Harry got a big chunk of Voldemort's personality downloaded into him as a baby, and Voldemort is a narcissistic, amoral, manipulative trainwreck of a human being. Petunia might have played a role, but I think the author's intent is that these are Voldemort's traits making themselves known.

One wonders, though, if perhaps Tom Riddle had a narcissistic caretaker in the orphanage that raised him. Unlike canon!Riddle, the MoR version doesn't seem to have been born a sociopath, but rather made one.