– It is quite slow to load on most pages. That's the biggest issue.

– The popup window with instructions get annoying after some uses, I suggest putting it more discrete as just a floating button with the text "Instructions" on the bottom of the screen.

– The tools menu needs descriptive text along with the icons. I couldn't understand easily what the icons meant.

– On my device, the stylus by default had a drawing function. I would prefer that the stylus could be used to turn pages just like a finger, or highlight text on long press.

– My stylus and many other stylus have a button for secondary "right click" functions. Maybe you could use this to bring up menus?

– In general I think a floating bottom menu with some basic functions would be more user friendly, especially for beginners. The menu could have a close button to be easily removed so that people can use gestures instead.

Like I suggested in the last thread about your project, I think you could make a great web browsing experience for Kindle devices, by combining your project with ebookmode: https://ebookmode.dropdatabase.es