^I think there are specific leather treatments for Nubuck leather. I think there is a brand called Apple (no, not that Apple) leather treatments online, which has products for Nubuck leather. They are not too expensive either I think. Maybe ask the people at the ACNE store? Maybe they can recommend a treatment.
Dying leather: When you dyed your leather jacket, you also dyed the metal (probably because it is easier). Have you figured out how to do it with the bag? Also, I think if the color is uneven on a leather jacket, it will still look good. It can give it a slightly distressed look, which can be great for that kind of jackets. On a stam bag however, I am not sure if the distressed look will be as great... Thats my two cents at least
Of course, I have not studied you leather jacket up close, and I can't judge how even the color is.
If you have these issues figured out, I would just do the math. Figure out how much you could sell it for, and how much it would cost to get a new black bag. You are not wearing it anyway, so it has no other value for you atm.