Kevin as I look at your pictures of the damged edge on the axe, it is my gut feeling that you have put too fine and edge on the axe, and did not leave enough support for the edge. Also the steel might be really brittle and hard on the tool steel inset, and fractured when it came up against a knot or other obstruction. Some knots are quite hard and can easily damage or take out a respectfully sized chunk of the blade edge. one type of wood that is really bad and that one should watch out for is Hemlock especially in a frozen state.
I personally like the edge on my broadaxe to be very sharp naturally, but as you leave the area of the cutting edge you should gain thickness gradually and be back to the full thickness of the tool steel inset at about 1.25".
Now all tool steel insets vary in thickness, The better ones are not real thick, and flow back nicely into the body steel of the axe head, and in many cases you can see the residual marks of the forging hammers as they folded and shaped the red hot steel creating the eye of the axe.
holding the axe loosely in your hands and striking it gently will create a ringing tone, and the sweeter the tone the better the steel and tempering.
I also use a good file to shape the edge if the steel tempering will accept filing, but as a note of caution if you can't file it then you have a really hard tool steel inset and it will be prone to chipping easily, now mind you it will cut great but you will need to use caution when using it around hard knots, especially dry hard wood like oak, or as I mentioned earlier hemlock