How often you can add a point depends on the frame rate of the video. You can try increasing the precision with FPS override feature, and hopefully you’ll be able to add a point precisely on the beat.
Tip: Equalize (hotkey E) is very handy for strokes with consistent interval. So long as the first and last action is in sync it will space out actions in between evenly.
So you just have to copy and paste to the end, make sure the last action is in sync with the beat, then select all points and equalize them.