Returning to original resolution and DPI

I have my S4 i9505 since july 2013, and the battery life was never exceptional, on the first year on lucky days I got maximum 4h SOT...

But as the time passed, the battery life got even worse, I tried the cm12.1 optimized roms, the battery life was slightly better, but the camera was garbage

Now I'm using the Imperium LL v9.1 ROM, and I'm getting around 2h30mins SOT, with around 9h of total life... (I take it off the charger 7h, put it again 16h... 17:30 I take it off, and 23:30 I have to charge again...)

So I tried to squeeze some more minutes by reducing the screen resolution and DPI, I tried using 720p with 294dpi via terminal emulator, it didn't seem too much pixelated to my eyes, but the touchwiz got a bit distorted, and the camera app was "zoomed" on the top left quarter....


Then I tried going back to the original resolution and dpi, using 1080x1920 and 441dpi... but the touchwiz is still distorted and the camera app is a bit off also....

Does anyone knows how to fix this distortion and the camera app, or at least, how to go back to the original resolution and dpi correctly?