Dead wood can be very hard.
Regarding losing the temper on the chain links, I think that, if anything, you may have done that with your sharpener. Very easy to do; if they turn blue, you've done it. I sharpen mine with a 5/32" round file, trying to take the same number of strokes on each tooth. It usually only takes three or four strokes if you don't let them get too dull.