I belong to J1. If anyone wants information about J1 subclades you should contact the J1 Project at FTDNA especially Mr Mas who does graphs of relatedness.
J-FGC4422 is the descendant of J-FGC4415. I don't know anything about FT350914. What I can tell you is the J-FGC4422 is the parent SNP of some Arabian tribes e.g Banu Ghamid, Al-Marri. I don't think it has anything to do with invasions, unless it was associated with the Islamic push after the death of the Prophet.