Kurt I'm sure more knowledgeable people will give you advice but I'll throw in my 2 cents.
1&2, 10 to 12 ft should be deep enough if you can pump cold well water in, but it would help to increase the O2 in the well water by running it down a short course of rocks to the pond.
3. In most cases an aerator is a big help but let the experts weigh in.
4. Catfish don't require as high a protein diet as trout, and I believe that catfish usually use sinking feed, so it's a matter of how much efficiency you want.
5.Yeah I would say no more than 50 in a quarter acre, but that also depends on what size you are stocking.
6. I have lots of GSH in my trout pond and they love them, and I'm sure Channel cats would make use of them also.
If you stock trout start off with rainbows, they're the most tolerant of warmer water but try to keep it under 70F.
Good luck, read up on as much info as possible.
