1. Parchment was very expensive and tend to smear whereas the more common Roman papyrus tended to crack. Just because it's used in a codex doesn't mean they were using the best type possible. In the end it was paper that dominated the codex format, not parchment.
2.
Burows of Norfolk experimented with comparing dibbling (planting in rows) vs broadcasting wheat, but he used a much lower sowing rate of 2 pecks per acre for dibbling (18.18 liters per acre). Despite the higher cost of sowing, the advantages in output, saved seeds, and easier weeding more than offsets this:
https://historum.com/proxy.php?image...2762340537d229
Both experiments still show greater profit for dibbling wheat than broadcasting it even if accounting for the cost of labour in sowing seed. The smaller profit difference is at least partially due to the much lower sowing rate he used (55 liters vs 18 liters per acre).
Also not accepting negative numbers is always wrong.
3. Long powerstroke crossbows allows Chinese low weight crossbows to match or exceed the power of many mechanically assisted European crossbows. Drawing a 2 stone crossbow is not necessarily harder than drawing a 600 lb crossbow with mechanical assist. Plus Chinese crossbows did use the mechanical assist of windlass and something similar to the goats foot lever during ancient times. So I would say they invented mechanical assist for hand drawn crossbows.
4. As I suspected, after reading the actual exchange between Zheng Wenfeng and his students, the professor was highly unhelpful and condescending towards his students with answers such as "Google it" without even providing what words to google when asked, ending the discussion with "doesn't matter, go waste your life".