UPDATE: HE ATE!!!

I have placed this update in a new thread for updates.
I just offered him a tiny pinky mouse, as instructed, and he nailed it! So he still has interest in eating. Now we just have to see if he keeps it down and, if so, digests it properly.

But the first step is a success!!!

Also, regarding Nagini (who refused her meal again tonight), I realized that she may be 'catching up' food wise because I was giving her mice as big around as her the last three times she ate. So, I'm not nearly as worried about her anymore either.