Are there any cover plates you can take off to look inside the bell housing?
Do you feel resistance as you press the clutch pedal?
If there is an external spring that holds the clutch pedal you could try removing that to see if the pedal "just falls down". If it does that would indicate a linkage problem.
Can you feel any feedback from the throwout bearing as you press the pedal?
I have no information about your specific tractor but have you searched for parts availability?
Most likely you are going to need to split the tractor to see what is going on inside. Splitting a tractor that size shouldn't be too big of a deal but I wouldn't want to start that project without knowing that a clutch package is readily available if I needed it. Throwout bearing and fork too.
If you do have to split it, take lots of pictures, not only for your own use but you could post some of them here to show the process for others to benefit from.
As a side note, the smaller Jinma 200 series have a habit of shearing the roll pin that holds the clutch lever to the shaft that goes through the bell housing. When you step on the pedal it only rotates on the shaft and never transfers any motion to the inside clutch rod. Put a witness mark across the lever and end of the shaft then step on the pedal and see if the shaft is actually turning with the pedal. At least that way you will know if the problem is inside the housing. Hope this helps.
Best of luck and please update this thread as you go.