Having analyzed your room quite thoroughly, I am completely certain that the most ideal location for your sub is to place it about 5 feet above the floor, just 2 feet to the right and 1 foot in front of the ideal listening position. I know it will be a little inconvenient to place the sub there, but trust me, it will be amazing.
What you could do is either hang the sub from the ceiling using heaving steel cables or chains. Or, you could build a 5 foot tall platform to set it on.
If you go with two subs, one should be 3.5 feet above the floor exactly 2 feet in front of the listener and the other should be 1 foot feet below the floor and 18 inches behind and 4 feet to the left of the listener. THAT, my friend, will be a killer system.
Let me know if you have any questions.