Differences in income and job performance would, by definition, play a role in the creation of socioeconomic disparities...
Is that a statement explicitly called out in the book, or your own inference?
Even if it's true that the book contains some inaccurate information, that doesn't provide a rational basis for one to assume that Murray is a racist.
No, but we're talking about whether or not it's reasonable to be critical of the use of racial disparities in IQ specifically in the sense of it being disparaging toward race. If noted scientists and philosophers can look at this book and judge in in that vein then I really don't see where we can rule out such criticism as completely unfounded.
I honestly don't see how you can infer from what she wrote that she's a racist. Nothing she said indicated any sort of hostility towards black people.
Like I said, balance of probabilities. Few people trudge out that "fact" unless it's part over some overall racist worldview. Listen, if I see a person wearing a white robe with a pointed hood and mask, I'm thinking KKK, not Spanish Easter Penitents.