Think a full tablespoon would be too much KL - I'd go with the 2 teaspoons per 500g myself otherwise your dough could taste too yeasty.
I keep my dry yeast in the freezer. I use it directly from the freezer as the couple of teaspoons you use soon warm up. I seem to have no problem with it becoming weaker that way, or maybe I use so much it doesn't have time to go off. Still hunting out somewhere I can buy fresh yeast though.
how did you stop the weevil plague Russell