Thermal Throttling Causing Unstable FPS On Android

My simple pixel-art 2D game is causing my LG G3 Android phone to thermal throttle. As a result, the framerate constantly alternates between 60 and 30 after a little bit, which causes very unsmooth gameplay.

Everything else about my game is good, e.g., the spikes aren't being caused by the garbage collector or poorly written scripts.

After hours of fiddling I was able to "solve" the issue by setting this in a Monobehaviour's Awake function:

 Screen.SetResolution(Screen.width / 2, Screen.height / 2, true, 60);

This cuts the phone's resolution (1440 x 2560) in half, and, as a result, cuts my game's graphics rendering workload in half, and then it is simply upscaled by the phone's hardware to fit the screen (?). This seems to have gotten rid of my thermal throttling and unstable FPS issue, but the graphics just don't seem quite as crisp...

I'm wondering if anyone knows a better way around this issue. Any tips or comments are appreciated!