If your chlorine test kit is not able to measure the chlorine, then it is probably safe for the fish. If the salt level is below 0.6% then the salinity is not a problem, unless you need to do a treatment for parasites, in which case the most commonly recommended treatment (malachite green with formalin, Proform C or equal) states on the label to not treat in conjunction with salt. I would use baking soda (gotten at Sam's Club or equivalent in 13 pound bags) to increase the alkalinity to a minimum of 150ppm as measured with KH test kit or otherwise to stabilize the pH. If I read correctly, you got their filters with the fish, which should be pretty close to mature for the fish load, which is good. Try to get it installed as soon as possible. As ws noted above, get and use the SeaChem Ammonia Alert Card to measure the toxicity of the ammonia. Water changes and filter cleanings should be performed weekly and the salinity will decrease with these by dilution. Normal recommendations are 10% water change a week. If other chemicals have been used like algaecides, then a treatment with potassium permanganate at 2ppm will kill/neutralize any biological products, making the water safe.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard