(5). "He (Wegener) claimed that Pangaea existed for millions of years, until, for some unknown reason, it broke into smaller continents, which then drifted, by some unknown process, to their current positions."

The reason may have been "unknown" when Wegener proposed his idea, but subsequent development of the theory of plate tectonics has moved on from the idea that a primative super-continent suddenly and inexplicably did anything. Does Mansfield's theory take account of present day records of movement on plate boundaries?

There never was nothing.