I'm so pleased I 'gotcha'. :) I've been hoping that my misdirection would be successful, as well as portraying a believable distress in Snape, and a maturity in Harry, give what had transpired.
Cuthbert was actually given by JKR as Binns' first name, very early in the series, but never officially. I thought it fit him, so I kept it.
I'm so pleased you liked it, and that end didn't disappoint. Your thoughful review was so appreciated!