@jaskobihac have you given "&thumbnail_size=" a try? you can see it for example in post.id section (routing file) - that lets you define the size to take (again, see without ?include and dev=1 for a list of all sizes your installation has available).
Indeed scrolling is not optimal - but the side menu should work. Do you get an error message in the console (Ripple) or with Logcat (adb)?
I might somewhen create a new JSON API based app as it's already a bit old and I had the chance to learn a lot more about JS in the meanwhile...but this can take ages (depending on free time :))
@ElevateMindz thank you. Believe in yourself and try again if you still need it - I'm sure you'd be able to manage it nowadays :)