Let the alk lower naturally. You will be fine.
Kalk is a balanced input source - it does both carbonate and calcium at the same time. If you need one or the other, then baking/washing soda and calcium carbonate is what you need.
Vibrant is basically an algaecide and some organic carbon (ethanol). The issue with organic carbon is that it strips the water column of available nitrogen in the form of ammonia/ammonium and corals basically are deprived. This is what people worry about with lower levels of residual nitrate, but this does not happen. To understand this, you have to step back a bit... corals get most of their nitrogen from ammonia/ammonium, not nitrate. The few that can use nitrate have to spend/waste energy converting it back to ammonia, which is not ideal... and not even all corals can do this. ...so the important thing is to have ammonia/ammonium available for corals to have. Enter Vibrant and other forms of organic carbon which cause waterborne bacteria to multiply - these bacteria will also consume ammonia and outcompete the corals. Whatever happens to the residual no3 levels is of no consequence. In the end, you want high availability through lots of fish feeding combined with lots of export to keep the residual levels from getting out of control. Without available nitrogen, it does not really matter what your no3 tests levels are.
