Thanks for the heads-up and for taking the time to provide such detailed feedback. I'm always happy to see players care enough for the game to share their thoughts about it.
I've already fixed the issue with existing saves in the default game pack. This should have never happened in the first place but looks like I didn't clear it after hotfixing another issue. This directly lead to point 4 of your list. Let's get through it top to bottom.
1) APK and the mobile version. I'm using a 3rd party packer for apks since default RPG Maker doesn't have this option from the box. The last version takes up 1.5 GB on my phone, not counting the apk for the install and I'm not sure why it gets 4 GB on yours.
The only advice I can give is to go for the desktop version if the mobile one doesn't meet your expectations. Since I'm a solo developer juggling real life with the gamedev, I can't learn and tackle all the fields. Mobile dev is not my chosen field and I made only after players requested it.
2) The difficulty is a tricky feature. You won't believe the amount of feedback where players find the game too hard to play or forced to grind a lot of levels before they can proceed with the story even at the current state of the game.
So, I'm quite reluctant to increase the difficulty, though I perfectly understand what are you talking about. I too prefer harder games like Dark Souls series, Blasphemous, etc. Yet these are not for everyone.
3) I'm not a native English speaker and mistakes do happen. While I proof-read all the texts some of them can duck under the radar. Send any errors you'll find (with a bit of info where did you encounter them) in the game and I'll look into these issues.
4) The save files from the default config affected your settings. This shouldn't happen if the game is shipped without existing save files just as it was planned. Sorry for the trouble.
5) Yes, the FAQ file was written part by part once the new feature got in Yorna. I'll see about tidying it up once I'll get the time.
Lewd level 5 is the maximum level where Ada counts as pure so you won't miss anything if you decide to reduce from a higher value