Hm... Can't tell for sure, but my guess would be female based on the head and the girth of the body. Females are a little more heavy-bodied than males.
I'm not great with IDing species I don't keep, but it looks like Thamnohpis radix to me (there are tons of crazy common names for the different garter species floating around out there)
Yeah, he mainly finds the food by smell. As he was going blind I got him to associate a touch on a certain part of his neck with food, so I usually have to cut the head off a mouse so he can smell the blood, touch it to his neck, and he'll eat. So far no one else has been able to get him to eat since he went blind, so I think he relies pretty heavily on that little ritual being done a certain way before he'll eat.
Eating is a good sign they're settling in. Sometimes just the stress of a move is enough to cause them to go off food for up to a month.