Sorry you were disappointed by 3 Frakkar. However, having had a visit from a friend who was wheat and gluten intolerant for a week, I think you are perhaps unrealistic in expecting restaurants to be able to guarantee a choice of several gluten-free dishes at any one time unless it's a specialist restaurant. And do remember that Iceland has to import a lot of its ingredients and foodstuffs ....

Glad that on balance you had a good time .... and ate well.