5.4 dKH is very low, IMO. 7-11 is fine, but I target towards the high end to give myself time to notice and respond to increased alkalinity consumption in the tank. That also gives my tanks a slight pH boost, which they need.
480ppm calcium is a bit high. I'd let it drop to 400-425, but 450 ppm is okay in general.
Baking soda is a fine alkalinity buffer, if you want to save some money. I would recommend going with a 2-part like B-Ionic or its DIY equivalent for long-term dosing. Limewater also works well, but it's a bit more involved as far as dosing, so you could wait a bit for that.