For a fish only tank nitrates of 40 are not that bad, but for a reef too high.
I never saw if you are using tap water or PO/DI water, if you are using tap then you need to stop, and use a pure water source.
I suggest you only use the cannister filter to circulate water and run the occasional bag of carbon or phosphate remover if necessary. With all your LR and your DSB you do not need all that stuff in the cannister filter. and if you do run carbon or phosphate sponge only leave a small amount in for 48hrs, remove it after that.
Other than that, for long term nitrate reduction look into a refugium with macro-algae, and be sure that sandbed of yours is full of the beneficial worms and stuff.
As far as feeding, sounds pretty good, except brine shrimp is like candy, taste good, no nutritional value, feed mysis and chopped up seafood from your grocery store, and occasionally feed brine shrimp.