As a mouse player that plays with 1300 dpi, I personally could/would never play with anything under 1000 just because its too much arm movement.
If you've already played 6 months at 800, chances are, you hitting a wall isn't due to your dpi. If you notice though that as you are playing maps with larger jumps and you are overshooting your aim, then maybe try decreasing your dpi to 700 or 600 (assuming if that is an option). If anything, the wall you are hitting is that you cannot read the harder maps as you have been increasing in skill, in which case, simply playing more will lead to you getting better, OR you arent focusing enough on your tapping/streaming accuracy and speed, in which case, play more and try to focus on getting better accuracy at bpms you are comfortable with, which will in turn help you become more comfortable at higher speeds
If you've already played 6 months at 800, chances are, you hitting a wall isn't due to your dpi. If you notice though that as you are playing maps with larger jumps and you are overshooting your aim, then maybe try decreasing your dpi to 700 or 600 (assuming if that is an option). If anything, the wall you are hitting is that you cannot read the harder maps as you have been increasing in skill, in which case, simply playing more will lead to you getting better, OR you arent focusing enough on your tapping/streaming accuracy and speed, in which case, play more and try to focus on getting better accuracy at bpms you are comfortable with, which will in turn help you become more comfortable at higher speeds