Story of surviving Shaolin monks and the founding of Hongmen

Are there any semi-evidences that the story about the surviving Shaolin monks and that they (indirectly) founded the Hongmen (The Brohterhood of the Hong or Hung)is true?

I'm not so interested about the part of the (five) Shaolin monks as I as a kung fu instructor heard this story already a 1000 times but more so about the founding of the Hongmen. What I'm still wondering is if the supposed founder of the Hongmen, Hong Xi Guan, is the same person who founded the Hung Gar (Hung Ka, Hung Jia, Hong quan) kung fu style and is better known under his Cantonese name Hung Hei Khoon.

Also, in the movie a monastery is named where the monks fled to and where the Hongmen was founded. What's the name of this monastery? They named it in the movie but I can't remember the name. Was this monastery later known as Southern Shaolin Monastery?

Thanks for you input.