I will try and answer your questions the best I can.
1) Yes alot of air in your bag is normal, mine was the same way. But after a while it calmed down and now it doesn't happen as frequently. If you are wearing a two piece system you can just pop the seal and release it, nothing to worry about.
2) Watery output is also normal. In the beginning after my ileostomy everything was constantly liquid, but after a while in thickened up. It will of course never be "normal consistency" but tooth paste consistency is what its like most of the time.
3) At first I did get a little sensation when the output would come out of my stoma, but I definately wouldn't call it pain. The only time I have had pain is when I ate to much lettuce and didn't chew it well. But if output is coming out and your not in severe pain then its probably ok. But you know your body better than anyone so if your concerned then call the nurse. Also the stoma will have output all the time....
I was also very weak for several weeks following my surgery. I think I had just been so sick that it just took me a litte longer to bounce back. Give yourself about a month and then you won't be able to sit still you will have so much energy.