As I promised (somewhere), I want to report how I got my Otterbox Defender off of my iPad. The Defender is pretty much shot (no one would pay much for it in its current dinged-up condition, but at least it is off my iPad.
(1) I removed the charging port cover (as normally done),
(2) I removed the black silicone cover (as normally done),
(3) I was able to pry the smaller half of the case (not the charging port cover) off of the iPad using a screwdriver and twisting it in the spaces where the two halves meet along the edges and on the outboard mating spaces of the back. It took several inserts/twists to move the small half. Fortunately I was able to do this without marring the iPad. This of course put dings/nicks in the plastic at the mating edges of the Otterbox, but what choice did I have (aside from leaving it on)?
(4) Once I got the smaller half off, I took a sheet of paper, folded about 3/8 of an inch on both long sides, and slid that sheet of paper between the front Otterbox facia and the front surface of the iPad screen. This was not easily done and it took some jimmying to get the paper most of the way in. And you cold hear the adhesive (or whatever that stuff is) breaking free as I jimmied the paper in. Once the sheet of paper was in, I could use the method advertised here to push the iPad out of the larger half of the cover.
All the pieces are intact, such that I wanted to, I could reinstall it. The mating edges are slightly nicked as described earlier, but nothing is really broken.
I think the lesson to be learned here is DO NOT USE a Zagg screen protector with the Otterbox Defender. Or if you do, place some sort of isolation between the screen protector and the Otterbox edge facia. It is entirely possible that if I had let the Zagg dry for several days (or maybe weeks) the two would not have adhered as they did, but I have no way of knowing that for sure, so be safe rather than sorry.
Thanks to all the folks that tried to help. Your efforts were not in vain as I learned other things from those as well.