Krissyg6, I been following your thread and understand your frustration with the 7500. When I bought mine years ago, I was quite disappointed burning straight corn, since it had clinkers knocking around the firepot and the stirrer was so filled that it was a drum instead of fingers. The stirrer also creates a lot of fly ash. Using oyster shell was the only way I could make it usable with corn. As the price of corn went up I blended 50% corn to 50% pellets and the clinker and fly ash went down. To me, the furnace runs best on 100% pellets.
A clinker pot will burn corn far better, but when AES built the 7500, they wanted more btu's than the 6500, and achieved that with a higher feed rate and the stirrer. Going without the stirrer will eventually flood the pot. A few have successfully made a clinker pot, which is deeper, but if I remember correctly, they can only run the furnace on the lower feed settings. I had thought about making a clinker pot back when I burned corn, but with pellets cheaper, I love the way the stirrer burns them completely.
I have no idea whether furnace cement or any other adhesive would fix your back board, but it seems the most you would lose would be the cost of the glue.