What is extraction site of a back molar supposed to look like after a week and what amount of pain am I supposed to have?

Depends. Typically, a blood clot will organize in the extraction site that will be replaced by soft tissue, and eventually with bone formation. The appearance of the extraction site one week post op may vary depending on the complexity of the extraction, and whether or not a dry socket is present. The level of discomfort likewise can vary, also dependent upon the above and individual perceptions of pain.
Varied. No pain. Varied appearance. Hole usually getting smaller. If pain, see oral surgeon not normal.