FYI, I ended up on this post because I got an itch mailer to notify me of updates to games and assets I am following and at the bottom this post was one of the three (random?) posts that gets highlighted from other game devs that I don't follow. I don't know how much of that mechanism usually sends traffic and I also don't know how you get a post featured in the emails but it got my attention. (I suspect it is random because I've never given the system any indication that I'm interested in visual novels as they aren't really my thing.)
From what I know of itch sales (by those who aren't high-profile developers) I think you've actually done quite well, especially with very little promotion, but I don't have a lot of data to go on (a few established developers from my country).
I really appreciate you sharing this data and your experience. Thank you.