You are very fortunate to like fish so much - you can pretty much eat as much as you want (sensibly cooked) and it can only be good for you (I really don't like fish). My only superpower in food is loving beans/legumes (I could live off them - which is both cheap and nutritious). Well at least in my country there is no lack of vitamin D unless you live and work in a lead screened bunker and never have to go outside (Australia).