Well, my name is Howard, is your name Jack? Oh well, it really doesn't matter.
Assuming the 20.5 green dot load is the 1 1/8th load and the 18.5 clays is the 1 ounce load I don't see a whole lot wrong. The loads you list should be snug, but not overly tight especially with 50 pounds of wad pressure. I have loaded up into the high 19s with the WAA12SL and clays, and loaded well up into the 23s with green dot and the WAA12 (I used to have a sadistic streak and needed to punish my shoulder badly) and did not have a lot of trouble.
The pellets are almost always just over the top of the wad petals, mine are too, 1/16th of an inch or a little less if I had to guess without measuring. If you have weighed the shot charge and it is within 50 grains or so of nominal I would not worry about the amount of shot at all. I would also assume you have weighed the powder charge and we can rest easy that it is within a tenth or two of a grain? If not I will have to break out my "you can NEVER trust bushing charts EVER" speach. Anyway continuing on, I am thinking that you are setting the crimp too deep and that is when and why the hull is buckling. I will go do some meausuring and try to give you some dimensions to look for on crimp depth and overalls and so on. Will post back in a few.