I don't think you killed your yeast. What was the temp of the water you rehydrated your yeast in? 95-105* F is recommended. And even if you did damage the yeast the second pack would take care of it.
What I am wondering about if your SG. 1.100 is high, like barleywine high. Did you use a kit? If so what were the fermentables in the kit and what was your batch size? If you are topping off with water at the end of your boil you might now have used enough. Or it could just be a mis-read of the hydrometer.
In the end, you will still have beer. Even if your wort really was 1.100 then it will take some time for the yeast to propagate and show signs of fermentation with such a high starting gravity.