Hi Michael and Welcome
Sorry for your losses. There is already good information here in this thread.
This is a good reference book article if you haven't found it already. Once your cycle is done, then likely there is more fun (uglies) in store, so at least this will mentally prepare you for what is standard when setting up new tank.
https://www.reef2reef.com/ams/the-supreme-guide-to-setting-up-a-saltwater-reef-aquarium.84/
Agree there are good discussions about some test kits not reaching zero, so you MAY be chasing false data. You mention of prime makes me suspect you are treating tap water - IF so then perhaps there are other nasties not treatable in your tap (think Flint Michigan) and therefore suggest RO/DI water to make salt, esp if wanting corals.
Good luck! This hobby tests all our BBAs - Bounce Back Abilities - good for life, good for tank. Hang in there and just take it slow