So I made some stats 
I used the transcripts from @Beyond_Sleepy here for chap 1 and here for chap 2, as well as the data for kanji by level in WK by @ChristopherFritz here, so thanks for that!!
I simply wrote a program that counts ALL the kanjis appearances (not the unique kanjis) and check at which levels they are learned, and pasted the data in Excel to have the graphs.
So to me, at a glance, it looks like the chapter 1 was a bit rough, with needing to be around level 24 to understand most kanjis, and chapter 2 a bit easier with most kanjis from level 13. Of course this doesn’t say anything about grammar etc, but I think it’s encouraging, will definitely try and verify my theory at level 24 