Do I need to adjust my Specific Gravity?

[Myka]

Yes, but not by very much...although I'm having difficulties wrapping my brain around that right now.

Ah, that's why it took so much salt. That's a lot of water volume. After the initial cycle, your tank should never have ammonia or nitrite. The presence of either is called a mini cycle, and means that you have done something to either damage the biofilter or you have added new critters which are demanding a bigger biofilter and it will take a bit of time for the biofilter to catch up.