Hi bro Five, yes the adapter could fail. If the light at the adapter does not light up...bring the adapter to Sim Lim Tower for a check....if confirm failed...then just buy a oem adapter there...cost around $25-$30
Seriously I have no clue whether it will work using refugium only....it also depends what type of corals(soft/lps/sps)...if SPS i doubt it will work as it is more delicate than others and couldnt take sudden shock....
The dosage suggested on the bottle serves as a general guide....but it really depends on your corals that you keep in your tank. But following the guide is a good start.