I wasn't sure I was going to get this finished, but lucky for me my whole family had other things to do today. With everyone gone, I was able to get in several hours of play and finish up with:
Total house values of $6,686,320 and 14 careers capped, for a multiplier of 2.4 and a total score of $16,047,168.
Unlike so many others, I have no idea how people managed over 20 careers. I can't wait to find out - every challenge I learn about new "secrets" that I had no clue about!