Yes, the section about "constant sitting".
I am not familiar enough with Tiantai to judge.Would you consider Ziporyn's discussion of that phrase in the review to be a fair representative of conventional reading of it?
Quoting only the section 法界對法界起法界 is not Ziporyn's idea, but Zhili's (see: T46n1928p706c11-12). Ziporyn discusses the passage in his review of Swanson's translation on p 20.
Not at all. On the one hand, you can take Madhyamaka as a different layer of teachings. On the other hand, not all abhidharma interpretations fall within the problematic points that Nagarjuna argued against.