1281??? Honestly I'm very impressed you got to that point - in testing i got completely overwhelmed around 700! I wanted it to scale fast so the game wouldnt drag, but also wanted it to not be over within a minute or two.
I had the timers between enemy spawns reducing every time you hit a multiple of 100 points, as well as a small chance to reduce the timer a tiny amount every time an enemy spawned, to have a slow but steady exponential difficulty increase. I knew there would be a break point, seems you found it!