1- Yes, seems very normal to me.
2- Interesting that you put edgy and paranoid togater in #2 because they are nearly always related. If you often tend to detect hostility in others there is a high likelihood that you are "projecting" it onto them. You could in fact be seeing what is in yourself. This is not always true, but it's worth taking a long hard look at.
3- This is VERY healthy IMO and an excellent sign of progress. Satisfiy this instinct with a well chosen subject. A sense of meaning and purpose is a powerful thing.
4- Likely not a big deal. Your body probably needs extra fluids but check with your doctor if you continue to have a concern.