To TRY to stop an active ferment you typically cold crash, rack, stabilize, sterile filter and typically keep wine in a cool climate. Difficult but some people accomplish it. Or you cold crash, rack, and fortify with a high proof liquor. Or pasteurize.
But in all reality the best thing you can do is allow the wine to ferment to as dry as it is going to go and then stabilize with k-meta plus sorbate and then back-sweeten.
That much sorbate can add an off-flavor to your wine, you definitely won't need to dose it with any additional sorbate at this point, unless of course your sorbate was old and expired.