You've been trying to use wrong programs.

ineptepub is used for EPUB ebooks from stores other other than B&N. The "Problem decrypting session key" for such ebooks is discussed in the following thread:
ineptepub.pyw error: Problem decrypting session key

For removing DRM from B&N ePub ebooks see the following thread :
How to remove DRM protection from B&N (Barnes & Noble) EPUB ebooks