BakerJ,
Lots of views but no replies as of yet so I will share what I can. The 3rd stamp in the top row is CSA #11 based on the broken lines above the "E" and "N" of cents and looks like the Milky Blue color. The pair is CSA 12 maybe a greenish blue color. NOTE: Identifying Colors based on scan is difficult but these would be my guess.
As for the stamps,you have no heavy hitters in the group, the Two cent(CSA 8) and the Twenty Cent(CSA 13) are cataloged higher in used condition. The first 2 stamps (CSA 4 and likely 7) are not great copies but serviceable. A little time looking at the sold lots on
ebay will help you see what similar material is being traded at.
The covers appear to be genuine uses and I believe them to be CSA 12s. The cover with the blue cancel is from Columbia, SC and has a charge box notation (513). If you are interested in the history aspects, you may want to look up the name Joseph Habersham. There was a Joseph Habersham who served as Mayor of Savannah in 1792. He also served as Postmaster General under Washington (1795 - 1801), although he died in 1815 long before this cover, one specific descendant, Josephine Clay Habersham, is remembered for her diary of Savannah in the Civil War. Not sure is this adds any value to the cover but it might be fun to research further. The cover is clean and the stamp has good margins.
Not much help on the second cover it is obviously a bit worn.
Hope this helps.
Hobsun