@EnkiSchmidt Thank you for taking the time to write such a thorough response! I've posted this before, but it deserves mention again: this forum contains the most friendly, helpful people I've ever encountered in a similar setting.
Your advice about taking away played status is solid gold. I just discovered what will happen if I do. The game took one Sim, whom I'd cheated into a Level 9 career in Education Administration, and turned him into a barista. While that was good for a laugh, it doesn't fit the story, so I had to cheat him back to his original career.
That raises another question, though. If I give a household Played status, what will happen to them while I'm not actively playing them? I've thought about MCCC. That might solve a number of issues.
It looks like I can cheat away many of the other issues. I can solve the weight gain with one drag of a slider in CAS.
I'm conflicted about what to do about the flirting. On the one hand, it could be fun for my "supporting characters" to find romance on their own. On the other, I'm seeing an absolute dramafest if my "main character" develops enough Charisma to enable the Enchanting Introduction. If he autonomously rolls that when I'm controlling someone else, he could create pink romance bars all over the world. Then, if I don't get rid of them, one of his long-forgotten former "flings" might appear out of nowhere, far into the future, and pitch a fit when he kisses his own wife.