I used Paint.Net to convert each page into 758x1024 in 8 Bit and the issue of blank pages has been resolved. Unfortunately, the pages still do not show full page. I have to zoom in to show it in full. Even so, when I go to the next page, it will automatically zoom out again.
Panel view still does not seem to work, even when I double tapped. I've added a video to show the issues I'm facing. I'm on the latest firmware (as you can see in the last part of the video)
EDIT: Got it working already! Was using an earlier version of Kindlegen that did not support Panel view.