I know it is hard to watch him lose weight like this, but most of your questions will be answered tomorrow when you see the people who will teach you how to feed him through the peg tube. If you still have any worries, this is the place to find answers for things that doctors can't tell you, so post often, read a lot, and ask questions as they occur to you. Hope we can help.
The tube is amazingly easy to use, but I feel like I would be doing you a disservice to try to explain it over an internet forum when you are so close to having a hands-on demonstration tomorrow.
Hang in there, it WILL get easier!

Andrea