Thanks.
I pulled out the splash guard, and ran several cups of ice through the disposer, alternating with a lemon and then an orange. I found I had to take a good old dish brush to the upper part of the disposer throat to get rid of old blackened grime, esp around the drain entry for the dishwasher. It's great to be able to see fully into the maw of the disposer with the guard off.
It was a little tricky getting it back in, but once I figured out how it wants to sit, no problem. There is one slight tear in one of the flanges of the guard, but otherwise it's in good condition. I am wondering where one can get a replacement.
I did find the probably cause of the jams. Chicken skin/meat cartilage seems to defeat this disposer. It turns into a big glob that resists chopping, and eventually it seems to jam the disposer in some way. I removed a big glob of it the other day, and another smaller glob today when the disposer jammed again. After that, it had no problem handling multiple cups of ice, lemons, oranges.