Alright, that’s definitely fast enough. I made that layout on my old Note 4 (Snapdragon 805), and it only scored 1380 realtics (with root & tweaks, 2180 with stock settings).
So. Weird issue, I just launched the game on my phone, and experienced no slowdowns/hiccups whatsoever (Galaxy S9+). I’d suggest you try a fixed cycles setting next, not too high, like cycles=40000 or so. That should more or less equal a decent pentium’s speed, but leave a lot of free cpu resources.