Sodium added by a water softener is a function of total grains per gallon of general hardness.
Water softening references are usually GPG (grains per gallon) of GH, which is close enough to dGH to be equivalent. When softened, the GPG of GH is converted to the sodium component with this formula: GPG of GH x .46 = sodium GPG. to convert the sodium GPG to ppm, use this formula: sodium GPG x 17.1 = sodium ppm.
So, your dGH is 10, which is 10 x .46 x 17.1 = ~80ppm sodium, or 40ppm given your 50/50 split. If you do a 50% w/c weekly, that 40ppm will stabilize at ~80ppm in a few weeks. In hydroponics, sodium levels of 30-100ppm are considered toxic, depending upon the plant.
As you can see, it is better to not use softened water. It is much better to have the 10 dGH (180ppm) in Ca and Mg than it is to have the 80ppm of sodium. Your water softener should have a bypass valve on it. I suggest that you do that when changing your tank water.
The KH levels are high, but should not pose too much of a problem. For plants, we prefer lower levels because the sweet spot for nutrient uptake is in the 5.8-6.2 pH range. A high KH moves you further from ideal nutrient uptake pH levels. There are ways to drive this down with various acids and this is being done by some members. However, it is safer to do it with RO water.