First off, on a 1.083 beer: did you bother to make a starter or pitch enough yeast to begin with? Its really hard to fix a beer if you underpitched. Usually, pitching extra yeast after you under pitched doesn't do much to help the problem. especially considering that most of the off flavors associated with underpitching happen during the first 72 hours or so of fermentation.
Second, unfortunately, usually the best chance to fix a "stuck" fermentation is the yeast at the bottom of the fermenter. So racking before a fermentation is finished is a bad idea. You may need to pitch a fresh slurry or active starter to get this one stated again.