Your tests seem ok but I'm wondering if they are accurate. Using the old water is a big mistake. You have plenty of bio available on the rocks and sand. Old water is just that, old water. I would have refilled using all new fresh mixed water. Set your skimmer wet and start doing daily water changes. They don't have to be huge, maybe 5g a day. Get a new mixing barrel, maybe a Brute 45g, and fill it up. You can take your 5g from that barrel and just add more water and salt to it daily. Keep a powerhead in it to mix the water.
I feel you are going to need to wait about 3 weeks to see where the tank stabilizes.