Boy, you guys are brutal when it comes to skills.
I'd use -1/-2, one target.
-1/-3 or -4 different targets
I have to shoot off-hand every other month and run through the qualification course quarterly. Shooting off-handed is not that difficult (with a little practice). Shooting (unsupported) and reloading with only the off-hand is a part of the timed qualification.
I shoot well with both eyes, but, when shooting off-hand, I bring the pistol over to use the eye normally used, anyway. The pistol is canted about 45 degrees from the bottom of the magazine well to the rear sight.
Shooting two pistols at one target is not difficult and seems to work out (more often than not). Shooting at two different targets gets a little crazy.
Remember, each "-1" is a huge percentage when throwing two bones. The "unskilled" levy suggested seems pretty stiff.
By the way, shoot with both eyes open, it helps pick up the next target and/or danger.
Just for kicks, I practice with revolvers, from time to time. Very slightly more difficult to sustain shooting while being on target when they don't have a single action. I find the movement of the trigger finger forward causes a bit of movement to take into consideration.