Mobile debug issues: bad quality, malfunctioning

Hi all,
I have just finished my mobile game and I have some questions about it. I started it as a PC, regarding target hardware, to make it easier to debug. As it is done now, I changed it to mobile and max quality. My mobile device is Cube U27GT-S tablet. It has a 1280 x 800 (16:10) resolution. My game consists only of widgets, it is a simple puzzle game. I did test the game on my PC using all the resolution settings, including this 16:10 and was fine. Now I have a very low res graphics with jagged edges on the tablet, and some of the buttons are no working, they act like they are not even there. I used the same settings on those as I did on other buttons, that work just fine. I did set the scalability to epic, all the way up.
The buttons not working are always the same ones, no matter if I build the game again and again.
The screen ratios are all messed up, even if they looked good on the 16:10 preview in the editor.
I need severe help here.
Edit: android version 4.4.2
I did set everything to Epic on scalability.