Gnostics were a diverse and rather heterodox group. I think trying to lump them all into one theology is disingenuous. Most of the books the Church disagreed with were destroyed by the Church, so we mostly know what the Church says the Gnostics believed. In other words, we are reading only the case made by the prosecution and not the defense. Pretty one-sided, don't you think?
Gnostics actually pre-date Christianity. Some Gnostic groups were attracted to early Christian proponents, especially to SS. Paul and John, in whom they found many of their own beliefs, because there are aspects in their writings that suggest the line between Gnostic beliefs and early hellenized Christian beliefs were not always clear cut, because Christian theology was not clearly defined for the first 300 years after Christ, especially regarding the nature of God, the concept of Trinity, and Mariology.
We could just as easily collect some of the contemporary saying and writings of various posters on FR, diverse Internet sites identified as Christian, or actual churches in existence today, and make comparable charts that show that an amazing array of what those who who call on Christ as their Savior believe regarding any of these topics, and the spectrum of the list would not be too far from what you posted.
Which Gnostic books "were destroyed by the Church"? And, why is it that what the Fathers said about the Gnostic can't be trusted?
To answer your question, I can't. The table seems to be a distillation of what the author says in the book. Fortunately, the book is online in Google. The table is found on Chapter 10 and may be accessed here.
Check out also the Bibliography and the chapter notes.
-Theo