I believe there is a character who has important info about Jon Snow. I am like %100 sure that he is a Targaryen, and whole story is based on that imo. If Jon dies that means , Ned's promise to Lyanna , Tower of Joy , and ever other question lingering in my mind for years were garbage,lol.
But yes, Jon doesn't have the unique appearance of a Targaryen, I believe thats because Targaryens mostly marry inside the house, and Targaryen appearance is least dominant among them. I think its going like ; Baratheon>Tully>Stark>Targaryen
All of Ned Stark's children has the appearance of a Tully, except Jon and Arya.
He mentions a whore's name to Robert as Jon's mother , well , it is what he promised to Lyanna I guess.
Besides, why would the Kingsguard defend ToJ when they can fucking guard Dany and his cunt brother, the answer is ; cus they were protecting the heir , Jon .