A 3.5" pump in 4" casing is a tight fit to start with. Usually at the water level the casing gets rusty and there is not enough room to get the pump through. However, you said it had a rope, which is never a good thing. The rope can break and wedge between the casing and pump. Hope you got out all the rope, maybe need to measure it. You could also have torque arresters, which are also not good. They can wedge and stick the pump. But I am guessing the rusted casing is the problem.
If you can get the pump back down, you can use a mirror to see down the well. Then you can run a brush down to clean off the rust, and the pump might come through. I have tried soap and acid and a lot of other stuff, but if the blockage is above the water level, these donít work very well.
Also if you can get the pipe to break at the pump, you can pound the pump to the bottom and just set a new pump above the old one. Is the pump set on steel pipe or plastic?