I say drive it.
IMO....the debris and particles are likely due to wear of the clutch plates, clutch discs, and band friction materials. It is likely that the trans is letting you know its time for a rebuild. The filter was doing it's job but continued use may cause addition wear of the clutch pistons, servos and accumulator pistons, governor pieces and the valve body spools and their respective bores. But....the choice is yours....rebuild it or run it....the longer you wait, will result in higher rebuild costs.....due to increased wear....just a thought.....
You should see what the A500 looked like inside in my 95 Dakota when I dropped the pan on it to install a new filter after the trans started making what sounded like fluid cavitation when putting it in reverse. That usually happens when the filter gets clogged up or so I was told. Anyways, I've never seen a more filthy transmission before. The pan was full of goop and crud. That was 10 years ago. Got to admit, I've been pretty mean to this old Dakota and am easier on it these days. Anyways. If you're not driving it much and don't abuse it, don't see why it won't keep on keeping on for a bit longer. How far away are the shows you want to go to? If they are local, I'd would attend if it were mine but you might drop the pan again after attending and see what shows up. If there's more junk in it, yeah, stop driving it for sure.
From the view of a failed friction element the issue had to be the rear band. The other issue is that line pressure in the transmission when selecting revers is almost double the pressure in the forward gears. If your filter was partially blocked maybe the line pressures were not high enough to hold reverse properly. Nice thi9ng about a torqueflite is they give you a pressure tap to check for pressure at every friction element. Who ever rebuilds the unit, I would defiantly have a pressure check done before taking it apart. Often a neglected part of the diagnosis.
