As is often the case, my problems turned out to be software compatibility issues:
Among other things, I have been using QuickMenu for some time now, and after some testing/troubleshooting, have identified that application to be the culprit of my Notification/LED issues.
After removing QuickMenu, my notifications work fine!
Keeping my fingers crossed that any/all other issues can be resolved via simple config change as well!
Back to "stress testing"
