2 Oscars need at least a 100 gallon (6ft) tank. You need a 75 at minimum just for 1. I agree that 60 feeders are way too many and will surely cause an ammonia spike.
Offering feeders is a good way to kill your Oscars. 1)they can get bloat from too much protein, 2) The more you feed them live foods, the meaner they will get, 3) unless you have raised a healthy stock of feeders yourself you take a good chance of introducing a disease to the tank.
For substrate, I started out with a bare tank and eventually went to sand. I think I would rather have gravel like I do in my other Oscar tank!
For a tall 75 just get a 90. Has the same footprint just taller.
P.S. never heard of there being an "Oscar Expert" on this forum. I'm getting another O sometime in the next week or two. Trying to figure out where it will go as it will be number 4!