Ok after more than a year here what I do:
1. Estract the images
2. Use this tool
https://wing-kai.github.io/epub-manga-creator/ to create a good fixed layout epub (this is better than Kindle Comic Creator because the resolution can get higher than 1280x800)
3. I send them here
https://www.amazon.it/sendtokindle (if my epub is more than 200mb I create multiple parts... usually I don't need to).
This way I can use the Kindle PC/Android app to read any manga even if I bough it on humble bundle (for example). Cover is still great on PC but it is limited by my onedrive account cloud space and there is no android version. Kindle PC/Android right now both got documents support (Kindle PC did not support documents 1 year ago) and the last version drm on Kindle PC can be removed. That's why right now this is my setup.
The main problems with other tools like KCC is that they use Panels instead of landscape double pages.
While I still don't know if there is any good epub fixed layout reader for android.