First of all, I completely agree with you on the issue of neologisms in the book. There is a vital thematic reason for the fictional vocabulary that only becomes clear 3/4 of the way through the book. I get the feeling that many who complain about this either a). didn't read that far, or b). entirely missed the point of the book.
People should go back and reread every quote from Fraa Jad. Such an exercise clearly reveals the core theme of the novel.
Also, I love that you read it aloud to your wife. After I completed the book, I asked my wife to read it aloud to me, and we are currently on page ~900 or so. It has been a very interesting experiment, and we have both enjoyed it!