First, let me say I'm very sorry I didn't see this comment until now. This was well before any updates, so I must have missed the notification.
All very good questions and I'll answer as best I can.
1) Harry 'eating' would be a euphemism for drinking some blood. I will try and make that clearer when I re-edit at some point.
2) Eddy wouldn't be able to heal himself. If you've read the other Unison Island stories where all the characters are introduced you'll see you never see a witch use magic on themselves. Also, Eddy is a teacher, his magic would be geared toward that job. He wouldn't be able to use anything else but the most basic spells for healing/fixing things. Thane only has the basic magic geared toward his job as a bodyguard/spy. His abilities include lock picking and bringing items to him from long distances - eg, if he has a box of tissues in a drawer at home he can summon them to him anywhere. Lastly, Thane's blood wouldn't work, he isn't a strong enough vampire and he isn't mated to Eddy yet. The same goes for Harry, he isn't old enough to be strong enough.
I will, of course,, make there clearer when/if I re-edit/expand this story. There is a plan to but things keep making me put it off.
Thank you for taking the time to read and comment