Yes, you could delete your ID. Disc tickets are not associated with any NNID (or console ID). They will work even if the console isn't associated with any NNIDs.But if you installed all your games (legit games without DLC) using the "brazilian method" using WUP (using the Web exploit and Homebrew Channel). Then could you delete yor old NNID or are these games attached to your that old account somehow?
Yes, you could delete your ID. Disc tickets are not associated with any NNID (or console ID). They will work even if the console isn't associated with any NNIDs.