Blank page after every image in most cases is caused by too big image height.
Calibre is
awesome but comic/manga processing there is very simple. I recommend you trying our
Kindle Comic Converter. Use
Other profile and set dimensions of your screen. If you will still getting blank pages/cut lower part that means your reader can't use 100% of screen in this mode. Experiment and decrease height until it will look good. Additionaly make sure that reader use margin configuration from EPUB file. I don't have idea if PRS-T3 is doing that by default or there is option for that.
If you find working settings let me know - I would love to add your device to our wiki.