calcium/alk issues..

[Maverick00]

so im struggling to get proper and consistent calcium alk and mag levels for the past few months. One of the big problems i realized i had was to many regular water changes which kept flushing the system of additives i keep measuring in. Im using brightwell aquatics reef code A and B i believe its called to try and balance the three. I tested my parameters tonight and found calcium sitting at 365ppm, Alk 13.2dHK, and Mag at 1130. My questions are whats the best way now to bring the Alk down and calcium up now that ive got the alkalinity so high, and once its there how are you suppose to maintain the levels especially after water changes which seem to lower all three levels (Instant Ocean) ? Or is it as simple as trial and error with constant parameter testing? Thanks for the help.