Your alkalinity seems really, really low. 80ppm equates to about 4.5 dKH and 40ppm would be 2.25 dKH. With levels that low I would suspect testing error or perhaps low salinity. What test kit are you using to test alkalinity? I would recommend Salifert or the Hanna Checker. You want your alkalinity between 7 dKH and 11 dKH. I typically shoot for 8-9 dKH right in the middle.
Also, is there a particular reason you're dosing calcium? You shouldn't need to dose anything as you don't have any corals and I don't see any coralline algae growing which would deplete your calcium.
Typically a good sign that your tank is ready for corals is coralline algae growing on the rocks and glass. It's not a requirement, just a good indicator that your tank can sustain coral growth.
Your nitrates seem a bit high but soft corals could likely handle those levels no problem.
Kudos to you for waiting so long before adding corals to the tank. Patience is key in this hobby and it sounds like you're taking that approach, but I don't think you're quite ready for coral yet.
I would recommend getting some decent test kits and verify your salinity, alkalinity, calcium and magnesium. What salt mix are you using? Are you mixing saltwater yourself or getting it from your local fish store? If you're getting it from your LFS you should still test the salinity at the very least to make sure it matches your tank. You want it to be between 1.024 and 1.026 specific gravity.
Once you get those parameters in order and can keep them consistent you should be ready for corals. A few water changes with a good salt mix should get you within the proper ranges in no time.
Let me know if you have any other questions. Good luck and happy reefing!
