Seeing as its extract the steeping temp really doesn't matter. Given the ingredients I would expect that yeast to get to a lower gravity. When I said calibrated hydrometer I meant does it read somewhere near 1.000 with tap water at room temp. This is just a simple way to see if your hydrometer is even close to being calibrated. Before you re-yeast there are a few things to try. First try to stir the more of the yeast back into suspension. Give the fermentor some agitation in some way which doesn't introduce a bunch of oxygen into the beer. Second, put the fermentor in a warmer place. When you move the fermentor and warm it up it will begin to show airlock activity, but this does not mean that it has begun fermenting again. This just caused by CO2 coming out of suspension in the beer. Give it 3-5 days and take another reading. If that doesn't work add more T58. Be sure to rehydrate the yeast before adding it to the beer. Follow the directions on the package. And do not aerate the beer before adding the yeast. This will cause more harm than good at this point. My guess is that you should be able to get it down 4-6 more gravity points, but 1.020 seems out of reach.