Jeep Grand Cherokee Serpentine belt problems.

I have a couple of questions. Basically, my belt broke on my 1997 jeep grand Cherokee. It runs on and across 7 or 8 big and small runner and work cogs.

One of the (runner) cogs broke internally and I have been looking to get a replacement in wreckers yards, etc. But that's a minor problem - however itseems to be the one that caused the bigger problem described below.

My problem is that the belt (i've cut it and tried to pull it out) has jammed itself behind the central spinning cog/wheel, the one that comes out of the engine block and spins the fan behind the radiator. I've tried turning this shaft and having someone try to pull th erest of the jammed belt out from behind but to no avail.
Question 1 then: Is is going to be a big job for a mechanic to take the radiator fan shaft apart and remove the jammed belt from between this shiny cog and the engine block? Would the whole radiator have to be loosened up?

Secondly. I have noticed that when I turn the engine now, nothing moves. None of the cogs. I had assumed that the driving power for the belt system came from the lowest, biggest cog. The one that is directly below the one that I talked about as being jammed. However, if this is the case then that should be moving when I run the engine, but it's not. So, this leads me to assume that the power to drive the belt system comes from the spinning cog which is jammed and sits on the shaft which goes to the fan at the radiator? The thing is that this doesn't look right as this is one of the smooth surfaced cogs which touch the smooth outside of the belt, whereas the cogs which work all the other pumps and alternator, etc, all sit inside the belt where they have multiple tracks and ridges running?
Am I correct in thinking that the main power that drives the belt is transferred to the outside of the belt via the smooth surface of the cog on the shaft that goes to the fan? (It just doesn't seem intuitively right, but it must be since that's the only one that is jammed and nothing else is moving?)

I'm going to have to bring it to someone anyway, but I would love to have the answers to these questions if you can help me? Thnx.

Also, finally, I have been able to lock a wrench onto what appears to be a large nut that sits around that shaft, and slowly turn it whilst having a friend try to pull the belt free as this thing moves and the shaft turns, but we haven't managed to get it out, although it did move somewhat. I could keep trying this, but I am wondering if by manually turning that shaft, is there a direction that might cause some problem inside the engine where it connects?
(Hopefully that questionmakes sense?) Hoefully I haven't done any likely damage by this manual turning of the shaft.

thnx much
KevinBecause if it hadn't broke the belt wouldn't have slipped and jammed elsewhere.