Question #1: Sure you can! If the baby is hungry, go ahead and feed her. She will let you know when she is full. At this early, you can't feed them enough.
Question #2: It may be that your milk is still adjusting. As babies drink more, your body produces more. So if last week she was eating a half of an ounce less, and this week a half of an ounce more, your body may still be transitioning into producing more. Don't worry too much about it-you're body will adjust.
Question #3: It is hard to tell when your baby is latched, but your breast tissue will be soft, not hard. When you are pumping, your milk will slow down to only a few drops. Just out of opinion, I don't think you can ever be fully empty.
Question #4: I did pump after my daughter was finished to reduce pressure. It helped, but I started to produce more milk that my daughter wouldn't eat. I eventually had to stop, as there was more than enough, and our freezer was full. If you do not pump, the only side effect is sore breasts, but that will ease away, as you will begin to only produce the amount your child needs.
Question #5: I truly did not know the answer to this when my daughter was that young. I still don't think I do. We fed her about 2-3 ounces every 2 hours. But, honestly, I used yahoo answers to answer that, and read what other Moms were doing. It was really helpful, and I didn't feel stupid asking the question, as no one was really judging me.
No one knows this stuff right off the bat. I don't know if you ever really know! It is just trial and error. You are a good Mom, and you are doing your best with a new baby. That is all you can do.
Hang in there, Mom!