Is it the uneven lengths or cosmetic blemishes hurting me

While I understand that the damage is cosmetic - as a past buyer and seller of Nordost cables I have found, and would expect, that any damage to the look and layout of the conductors is simply unacceptable -- there's plenty of other cables available without these issues. 

As others have suggested your best bet is to split the longer length and sell this as a 7' pair with the other piece thrown in for free -- frankly I think you'd get as good as if not a better price then you're currently aiming for with this combo.

Which is one of the reasons I moved away from Nordost ... lousy ongoing support. Audio quest will determinate or cut down any length of their cables at cost whenever you want. I’ve had a 12m balanced converted to three shorter cables, and then had two of these re-terminated single ended with no problems. 

As as others suggest any competent cable engineer can do the work for you. I use Mike at Verastarr when I need this sort of work done. He will give you a good price and he works quickly.