Jim R you have the same parking brake set-up as I do. Is your NX a non-cab model also? It's interesting you have very little wear on the brake parts - from your description you are using the exact same sequence which I have always used - cram the brake pedals down hard then push the locking lever down to engage the pawl. To release just step hard on the brake pedals and the locking lever springs off - which is where I believe the wear occurs. Maybe I use the parking brake more often than you. In a typical day of using the tractor for, say, brush clearing or even mowing I might use the parking brake dozens of times - every time I get off the tractor whether I leave it running or not. Of course now that it is so worn I can't use it at all. When I do eventually replace or rebuild the parts I'll be sure and modify them so they will last.
And I'm mystified as to why I'm having so much trouble attaching photos to this site. Every time I try I get an "invalid content" message or some such on the attachment procedure window.