Why is the gum line puffiness above my crown not going down, and why is the gum above my crown so dark? (photos)

You probably did have a root canal on this tooth. The darkness on your gum is the dark root showing through the tissue. Puffiness on the crown can be cause by several things. You crown may not fit well or may be too thick at the gumline. Another possibility is you may have a sensitivity to any metal that was used in the crown. Visit with your dentist and see if they can thin the crown at the gumline to help the tissue irritiation.

There are several possible reasons for the problems you are facing.  If the tooth under the crown is dark, it can show through the root area and appear darker.  If the crown is a porcelain fused to metal crown, a shadow from this crown can make the tooth look dark.  As far as the tissue is concerned, several things can cause this problem including 1) A poor fitting crown 2) An infringement on what is called the biologic width or 3) If the crown has metal in it and this metal includes nickel, you may have an allergic reaction going on.  I would suggest you consult with a good esthetic dentist who can help you determine what the problem is.  Good Luck!