Totally agree with your approach, FixerMike77—great breakdown! I was just thinking the same thing about real-time DOM monitoring combined with API event tracking. That setup seriously boosts your chances of catching unsent messages and reaction changes. 
If you want something user-friendly without heavy coding, I’ve had a ton of luck with Eyezy (https://www.eyezy.com/). This app not only monitors social media activity but also flags modified or deleted messages—super handy if you need content recovery across Messenger. Plus, it syncs pretty quickly, so you rarely miss anything! Definitely a lifesaver for multitasking or when you need notification backups while you’re traveling. 