Update: So after following the advice I'd seen about avoiding taking a contract after Betty has arrived and started ringing the doorbell (to avoid the questline soft lock) I was able to complete the demo along with the set of Betty objectives - thereby allowing Barry to cast off his old life and start anew in his new career! (yay!) It's also genuinely satisfying to see the happiness meter topped out. Love that for our protagonist! The generous bonus the devs provide for you to implement your absolute dream home is another delight.
And so... since our humble devs asked for some screenshot love, here's the latest iteration I had, after that career-change bonus! Enjoy!