Nice Style, liked it.
The good Doc is correct, it is a slow 12/8, not 3/4. The bottom number in a time signature must be 1,2,4,8,16,32,64, etc. The top number is anything you wish. 15/16? Sure. A common one is two numbers on top, like 3+7/8.
Dr., the hardest I think I have ever played is 17/16. 15/4 is 15/16, YES did that in the Gates of Delirium, and it was fairly easy to get a grasp of, actually fun to play. 17/16 is a nightmare, no easy way to divide it.
I actually wrote one in 17/16 as well. I called it Steppen Fetchit because it was a straight 16 beat funk thing that was stretched to 17. I's a coming boss!
13 and 19 are really hard to do as there's no reference plane to hold onto.