Im confused...Ok,So the crankshaft is turning? You pulled the barrel up over the studs yes? Your not trying to turn the piston in the barrel,you will damage the conrod,your just trying to get the barrel free from the crankcase

Just relift the barrel over the studs. Remove the 4 crank case bolts completely. Remove the blade boss and seperate the 2 halves. BUT. You need to take the flywheel off,coil plate cam and blade boss or your wasting your time,and risking damage to other parts. Clear everything away.
The images show me that the barrel is definately a model 1 as is the head(full model 1 engine) You now need to be very careful as parts dont come easy.. Your main aim is to get it apart without damaging anything but the piston. Just do it step by step and ask questions whenever you like:) read the process in the victa book,should be pretty much the same as the steps for the later 125. And NO the conrod isnt readily available,and rarely sold seperatley from a complete engine.