Well I'd sort of go with huesmann's suggestion, but instead of using EC-1118, I'd try with K1V-1116 first - oh and google for restarting fermenation/stuck fermentation first for the method to actually use.....
Depending on the starting gravity, it's possible to make the batch hit 18% ABV if there was enough sugar's in the original must (a potential of 18% ABV in a must is a starting gravity of about 1.135 or so).