First, that "click" you heard could be a squib that is jammed in the forcing cone. Try shining a flashlight on the B/C gap and see if you can see an air gap in this area. You may also want to take a thin shim and see if it will pass completely through the B/C gap, I suggest using a 0.003 inch valve shim. If you do have a sqib lodged in the BC/ gap you should be able to drive it back into the cylinder with a hardwood dowel. However be very careful you don't allow the muzzle to point in any unsafe direction while doing this.
I have to ask how much force you applied to the cylinder and in which direction you tried to rotate it. On this early model you should have been turning it in a clockwise direction with that card blocking the cylinder stop. I would also suggest that you push the trigger forward before starting, this should release the hand from the ratchet. It may also take a bit more force than you applied, however how much force to apply is admittedly a matter of judgement.
Second, take a good close look at the unfired rounds in the cylinder, specifically look to see if by some chance you have a cartridge that was way over the length specification and has a bullet poking out the front of the cylinder. In this case if that "long" round is jammed into the barrel, using that card on the cylinder stop and a bit more force to get that bullet clear of the barrel should allow you to get the cylinder open. What you will want to do is rotate the cylinder so that "long" round is opposite the barrel, there is plenty of additional clearance in this area and you'll then be able to open the cylinder. NOTE, turn the cylinder clockwise in this case.
You didn't mention if the cylinder release will move either forward or back. It's possible that the bolt that the cylinder release is attached to has broken and is jamming the hammer. In that case it's likely you'll find the cylinder release won't move in either direction. In this case you'll have to remove the sideplate and then the hammer to gain access to the bolt.
If the cylinder release will move forward and spring back normally, I would suspect 2 possible problems.
One is that you have an ejector rod that has really wedged itself in or powder under the extractor has jammed the extractor into the recoil shield. If this is the case a bit more force may free it up.
Second possibility is that that hand has broken and it's wedged into the ratchet. If that is the case the only option is to remove the sideplate and pry it free from inside the lockwork.
Obviously, with a loaded gun you'll want to be extremely careful about insuring the muzzle is always pointed in a safe direction. If you have a sandbank or some sort of dirt berm available, I would urge you to use that to insure complete safety in the rare event the gun fires. I would also suggest using a faceguard and wearing good leather work gloves. While I can't forsee your doing anything to cause the gun to fire, it never hurts to be too safe.
If you don't know the lockwork in these guns with your eyes closed, I would suggest that you try and find a local gunsmith familiar with S&W revolvers. Fact is there is always some risk to trying to repair a loaded firearm and it's far safer to pay a professional to fix it. In addition, if you were to injure yourself it will prove to be a lot more expensive that paying a gunsmith to repair it.