Oscar fish professionals please!?

I can not answer all of your questions, but from my experience of owning Oscars, the Oscars get to know you pretty quickly, and have very good eyesight, they can see that can of pellets from across the room. I tried feeding my Oscar bugs from outside, and they got a funky fungus that put big holes in their flesh. I was able to clear it with some over the counter meds, but it was pretty disgusting. I would not feed them house flys, if you want to feed them something live, get some feeder fish, they will love that. I never tried putting ping pong in the tank, but I heard some love it. I imagine if you put the ball in when you feed it, it will learn to ociate food with the ball, and therefore play with the ball. I used to hold the food about an inch over the water, and shamu style, they would jump out & take it from my hands. Once a week water changes should be 20% of the water, so 6 gallons for a 30 gallon tank. I love ornate tanks, but as my oscars got bigger, they knocked everything over and lifted all my fake plants, I'm sure they had fun doing it, but if you are going for an ornate look, you are going to end up with a tank that looks like a tornado went through it.