The 99 D Lincoln also has what looks like a point coming from the MM. Yours looks like a die crack, neat find! The 99 I thought originally was a plating blister, then after finding more of them, it looks like a small die chip.
Pretty sure the “horn” off the 58D is not a die crack. Probably a die gouge or something along those lines. Not a crack though.
I am not sure about that. It could be either. The 52 D has what is known as a winged D. There are many progressions of that particular die chip. But, yes it could be a die gouge.