Bolsen, are you SURE that ALL the water you use goes through the softener? Lots of times the kitchen sink is bypassed for health reasons. Outside faucet?
Just thinking out loud here. It's generally not a good idea to use softener water in aquariums.
Baking soda would add MORE sodium, so I would look for a calcium substitute, which would raise alkalinity and pH. Try Prestone Heat Driveway Melt (yes I'm serious - it's pure calcium chloride). Google for instructions in aquarium use.