Once again I am floored by the amount of information in this post. As you have told us that your hubby is your researcher but I can imagine the amount of effort you guys put in collecting all this together.
I am a bit ashamed to admit that I had never heard of Yuan-Chuang before, or if I had then I do cannot recollect now. Its a bit of double whammy knowing that I have already lived and been to some of the places that are mentioned in his journey. I am a bit of a history nerd, so I usually have a bit of a clue about subcontinent's history...... this time though, nothing.
There are so many things in this post that I would like to talk more about (particularly his travels) but there were two things that I could especially understand from other references that I have previously come across.
First one: Are the 36 texts on Logic (Yin-Lun). I have found that in theological studies, the sections dedicated to logic is an integral part of studies no matter the religion or faith. To the most extent this always seemed a bit contradictory to me and yet it really wasn't the case. Back in the East, they have their own philosophy about reasoning and inference while most of us are traditionally exposed to references in the matter which are derived from the ancient Greece. I couldn't be sure but this could have been the source of confusion for me.
Second is the mention of monks of both vehicles in section 4. I really liked the coexistence of both Hinayana and Mahayana together under one roof. Of course, as you mention that this might have been possible to some extent due to Mahayanist monks having no particular monastic code but nevertheless the doctrinal differences would have generated some friction. Yet the idea of their coexistence seemed very 'India like' :-)