A teaspoon is 5ml. At 0.92g/ml and 9kcal/g that would mean about 40kcal per teaspoon.

I think you mean table spoon, which is often enough dressing for one person, in my experience.

Sure, but the rest of the stuff (in what I consider salad base - tomatoes, cucumbers, maybe peppers?) is really small so it doesn't matter. A greek salad has cheese, yeah, that's a high calorie input but you don't eat much of it