Your fermentation is not stuck. Windsor cannot ferment maltotriose, which is why you have a high terminal gravity (i.e., Windsor is not the best yeast strain to use with beer styles above 10 to 11 Plato). You have to deal with a double whammy at this point in that you cannot vigorously aerate a batch that is currently sitting at over 7% ABV. My suggestion is to pitch 20 grams of the yeast strain that I like to refer to as the Terminator (a.k.a. K1V-1116 or Montpellier). K1V-1116 (Lalvin K1-V1116) is one of the best kept secrets in high gravity brewing. Unlike most wine yeast strains, K1V can ferment maltotriose. K1V is an S. cerevisiae wine strain that is good to 18%. It also emits a killer toxin that inhibits all other microflora in the fermentation; hence, the name Terminator. Best of all, K1V is well known for its ability to restart a stalled or under attenuated high gravity fermentation. K1V is POF- (phenolic off-flavor negative).