looks like you've done your homework.
i think these tanks are challenging in the first couple months until the system stabilizes, floating plants help during that phase to absorb extra nutrients. I'm in the 6th week of my walstad but i cant trust my tank. amazons are doing good. crypt is doing nothing (its static, not growing, not wilting), cabomba - cant say. another stem plant is also not doing too well. i lost a guppy for unknown reasons - must be bad water or spikes. my tank gets partial sunlight off and on during the day, i dont have any algae, water is clear.
walstad recommends soil layer thickness not greater than 1inch after you've pressed it down. maybe you want a 0.75 inch sand cap? reason is that if its not thick enough the soil will want to come into the water. also think on the lines that you will not be able to move plants around much after everythings setup - it gives up too much mud into the water, not that you cant deal with it.
I wouldnt add fish until your water params read right. I've had 1 fish death. But the reason could be that I dont have Miracle Gro available in my country, had to use garden soil, no other option.
i cant comment on your lighting. IME a smaller lamp, with smaller surface area is better than a lamp with larger surface area of the same wattage/lumens. then you are imitating the sun. my plants have done well with the smaller surface area lamp.
your fish & plant stocking lists sound right. good luck, do keep us posted, you can PM me too.