Am I cooking frozen fish safely?
Freezing kills the parasites in fish that are harmfully to humans.  That is why all sushi fish has to be frozen before use.  Since the salmon is frozen and has spent way longer than the minimum time frozen you could consume the fish raw with no danger to yourself.  You could have added the fish frozen to your sauce if you had wanted.  

That said, I almost always thaw frozen fish at low power in the microwave so that it is easier to work with.