I built my first press a couple months ago and learned from trial and error, i'll elaborate where I can:
1) i used a basket style of press. I wanted to make sure that my cheeses (singular in my case) didnt slide around and topple like i've read in other articles
2) with a basket, I would say yes. without a basket you might be able to press faster. That said, half the fun of pressing day is getting the neighbors together to hang out and have a good time. Speed for me anyway, isnt a factor.
3) I put sodium metabisulfite into my must as the apples are ground up. I put way WAY too much in this year though and the juice never oxidized, and I still had some issues with getting fermentation to kick off. I put 1tsp per 2-3 gallons of ground applesauce where in reality I should have used somewhere like 1/4-1/2 teaspoon worth for a full 5 gallon bucket of must. If you add your campden after pressing, I would think the 1 tab per gallon of juice would be sufficient to store it for a week to keep it from oxidizing.
4) You cant. garbage disposals have nooks and crannies everywhere. They werent made to clean up afterward and reuse them for food prep. My best advice to you would be to run it with the garden hose running water through it, then afterwards, use a bleach solution to rinse it out as best you can. then store it for the next pressing. Before the next pressing, the apples should be dried and should flake off right away. turn it on, let the dried bits fall out/shoot out of it. then run a good few gallons of hot water through it and finally sanitize right before you're ready to puree.
5) not sure what you're getting at but i'm sure there are food safe bags to line 5 gallon buckets with at a resturaunt supply shop.
6) Most silicone is NOT safe for food use. You need specialized caulking to come in contact with your food. the resturaunt supply will hook you up with this as well. Side note, it'll take a few weeks to properly harden and bits can still flake off into your juice. Personally I just built my press tray out of oak flooring and once I pressed enough apples, the wood had swelled enough to seal up any cracks. anything larger, the bits of apple sealed them in eventually.
7) not sure, cant comment, I dont use any bottom plates. I use all wood in my rig.
8) I was able to press a full basket (about a 5 gallon bucket worth) of fuji apples in about 30-45 minutes, and i consider that rushing it. I would give each 5 gallon press a good hour. Press it down, let the juice drain, every 5-10 minutes, go check it and if it needs more, then press it down again.
9) cant comment, never used a whizbang.