Game of Thrones R+L=D and B+A=J ? An Alternate Jon Snow / Dany Theory

What really happened at the Tower of Joy? Most of us buy into the ASOIAF / Game of Thrones fan theory R+L=J, but is there evidence to support another theory, R+L=D and that Jon Snow was not the result of Rhaegar Targaryen and Lyanna Stark? If so could B+A=J be the truth? I go over it here, Discuss!