I eat it once a month max. All big fish have toxins (they climb up the food chain)
There's a common myth that a fish/seafood and cheese combination is not a thing, particularly in Italy. Several regions across Italy have fish/cheese dishes. Personally was never a fan of the combo until I recently gave a well made tuna melt a shot. Legitimately damn good. As habsy said, if you dislike it you've likely been doing it wrong. And frankly I only tried it once or twice before and they were not done properly.