I purchased a refugium starter kit from @AlgaeBarn and finally got some pods seeded and growing in the tank. I plan on seeding more every other month with as many different species as possible for diversity and won’t probably even think about adding a mandarin for at least a year.I think that looks like a good stocking list, I've currently got 7 fish in my 40 breeder (display being smaller than yours). It doesn't seem like too much for my tank and you've done a good job and parsing out their habitats.
Have you purchased any pods (amphipods/copepods) to start seeding the tank with? I would highly recommend doing this before you put too many other fish in the aquarium. Feeding phytoplankton and small particulate coral food will allow them a few weeks to set up a good breeding population before anything predatory towards them ends up in the aquarium. This will also help long term in your mandarin care, I'm at ~4 months with my aquarium and I would be more than comfortable adding a mandarin, I have pods coming out of my ears right now haha.