Welcome! Sorry to hear about your troubles starting up, but it does get easier (and then more complicated). The thing I've learned is to treat it as a science. Everything is a variable, and the more variables you change at a time the more uncertain you are about what is causing what. So do this, pick one thing to focus on and change it. Then wait, see what happens, give it time to have an affect. Then move on to the next one.
IMO, with that few fish and corals you don't need to be dosing anything. If you're doing regular water changes with a good salt mix then the water change will take care of any trace elements you need. You just don't have anything in your tank yet that is really consuming these. That will change as you add more life to your tank.
Depending on what you want to keep, start with some simple, hardy fish and corals and slowly increase the load. Green Star Polyps (GSP) are cheap, hardy, and pretty to look at. You can find a few people selling them on here for $5 or so. Mushrooms are good as well. Just make sure you don't put either directly on your live rock or they can grow out of control, so put them on a small piece of rock on your sand as an "island". Xenia and some of the leathers are also generally good starters. When you introduce new corals start with them on the sand bed furthest from the light, see how they do. If you want them higher in the tank then slowly raise them over weeks so that they can acclimate.
So what I would do:
Stop dosing anything
Cut back on feeding to at most 1x per day (until you add more life you're just feeding it into your skimmer)
Remove the filter
Bring your salinity up to 1.025
Continue doing 5-10g water changes weekly.
Start logging your water conditions daily. Once they stabilize, log every other day, weekly, etc.
This will get you to a good baseline where your tank is stable.
Slowly add life. Cleaner crews (hermits, snails) are a good start and will help condition your tank.
Next I'd add some mushrooms or GSP.
If all goes well, maybe try another fish.
Let us know how things progress,