It is not clear why the MC and his EX broke up ... I would like to know that cuz they seem to have everything good physically well packed and both wealthy (or at least with stable income) ...
+ I would LOOOOOVE more content with georgina <3 dat girl is fiiiiire XD I got many game over because of her hahahaha (like when the daughter asks you to cancel your date with georgina cuz she'll be leaving in the next few days OR when GG invited both of u to her house hhhhh)
Ultimately, they separated because they had some key differences imo. Rachel is more material, and lives her life trying to control things, and she often makes choices out of fear of what might happen. She is a planner more than MC, and thus ultimately took that controlling path that made her more successful materially.
MC is almost the opposite. Living with Rachel and observing her world views ultimately caused the two to clash. We know MC can have outbursts of anger, which adds gas to the fear/control issues of Rachel. Thus their relationship was doomed - and over time, they grew further apart.
Brad is a symptom and not a cause of their problems.