Twin Mountain is a tough one. It's one of the best places in the Whites in terms of views, solitude, trail access, etc. But it doesn't have much going on to support restaurants. Hikers alone will never keep a business alive there. I'm no businessman, but I think for a restaurant to make it there, it may need to have multiple revenue sources so it can rely on something else when profits from food are down. Personally, I would put Twin Mountain pretty close to the top of the list in terms of desirability from a hiker's perspective.
And yes, the gas station. Quite a collection of posters. I have a few favorites. They have always been courteous to me, however I do feel as though I am being watched in case I try to steal a dusty can of pork and beans. There were about 6 cans on a nearly empty shelf when I was last in there and they were way overpriced for gas. Get coffee, make little eye contact. Approach in non-threatening manner. They used to have a sub shop in the back that was half decent.
That said, in line with PB's comments, my most consistent meal over the years in Twin Mountain has been a coffee and muffin on the gas station porch. Eat quickly though, and watch for little red dots moving about.