Barry, the handlebar clutch normally only operates the drum clutch, controlling forward movement. The park/drive lever stops everything (reel and drum), by relaxing the tension on the belt that drives everything. I've never seen one like yours. We can see if anyone else has seen one like that, but the mechanism looks home-made. I'm wondering if it is not the previous "tenant's improvements" which have left you with something not very usable. Deejay, have you seen anything like this belt drive?

If the reel is stuck either it is adjusted too close to the bedknife, or the reel bearings have seized. You might check the adjustment before pulling the reel out.