Tassod, I know it is frustrating sometimes when things don't go as expected but it is part of the learning process and I hope you still are enjoying the build. I know at the end, all the frustration will be worth it when you have a beautiful reef tank going.
When I started to cycle my tank, I have everything put together: aquascape, sand, fuge, protein skimmer...etc in freshly made saltwater at operating temp. Once the cycle is complete, do a 50% water change and you can start putting a couple of hardy fish in the tank and begin adding clean up crews. You don't want to add new sand or rocks after the cycle is complete because new sand and rocks may start another mini cycle which you want to avoid.
What does your fuge consist of? What do you have in it?
When I cycled, I have about 4" of sand and some live rock rubbles in the fuge. No chaeto which was added much later after the tank cycled.
You don't need to have lights on when cycling. I did with my DT because I love to look at my tank with lights on even with nothing in it. If you don't have chaeto in the fuge, no light.
Tassod, good job with your mixing station. I wish I have space to do somthing like this. Mine is in the garage about 20 ft from the nearest tank.
The trick with a system like this is to make sure you have a fail safe procedure so you don't dump a whole barrel of RODI water into your sump before you realize you turn on the wrong valve(s). Since your tank is on the other side of the wall, you need a quick way to turn off the pump remotely from the tank side.
What did you use to enter the brutes? They don't look like bulkheads, are they uniseals?