Nitpick/clarification: Torque is (radius * perpendicular force), so I’d write “inch-pounds”. IMO, “in/lbs” is misleading, as in “inches per pounds” which is incorrect. Maybe it’s notation that I’m just not familiar with, but I thought it was worth pointing out.
I don’t think that a torque wrench is the best rig to get data with in this situation, unless you all have far more sensitive torque wrenches than I do. I would recommend a rig like this: Picture something like a standard ratchet (Like this) welded into a single rigid body. Set this on a table top with the “socket” pointing up and the whole thing able to rotate freely about the socket. Attach a fish scale to the end of the “wrench”, turn the “socket” as hard as you can, and calculate the torque. This is the torque that you can apply directly. Ideally, the “socket” would be in the shape of a nut, so as to more accurately reproduce the OP’s question. If it weren’t finals/moving out time, I’d try to rig up something tonight. Instead, I’ll leave it as an exercise for the students. 
Then you calculate the wrench-assisted torque, which will be different for different
lengths of wrench. This is a simple matter of how much force you want to apply. For example: I weigh about 220 lbs. So if I stood on a 2 foot wrench, I’d apply up to 440 footpounds of torque. I’d never do that, however, since that would strip most standard size nuts and bolts. This is where your torque wrench comes in handy. You can determine some sort of practical maximum torque that can be applied. Tada!