Somewhere on this website Bill Cody wrote about the life cycle of a pond. I can't find it and wish he would do it again. It sounds like yours is past old age and needs a new start. I expect the big cats died of old age. I expect that the bass were not properly harvested and now you are bass heavy. Other fish, crappie, etc., have been arbitrarily added. I see no quick fixes to your situation.
You can possibly harvest your way out of your present situation. Keep every bass under 14 inches, keep all of the crappie, and keep trotlining carp. The remaining bass will grow when competition decreases. However, with bass present, I think you are mostly out of luck on spawning of catfish. To deepen the water, it makes more $ sense to raise the dam.
All that said, I would probably suck it dry, clean it out and start over. Fifteen+ ft. is a lot of muck. I believe you will be a lot happier 3 to 5 years down the road with a fresh start. You could place structure where you want it, build ridges and start with known species. You might consider a separate forage pond for raising of catfish to be added as they grew. BTW, if you do suck it dry, you might be surprised at the size of the bass and catfish that are remaining. However, if they won't bite, I consider them useless.
