Congrats!!!!
Isn’t it fun finding new ways to drive yourself crazy?
40 bpms is the minimum speed for most metronomes… One thing you could do is to change to 80 bpms and doing two beats per circle, so you are at the same speed. (Essentially,. nothing’s changed.) That will allow you to experiment with slowing things down. For example, you could find the minimum speed that you can edge at, and then force yourself to try five or ten minutes at a speed just below that. 😉