Thanks, Nathan. I'd seen that set of instructions but since it involved installing android studio I didn't feel like following it at first. I have just done so, though, and now Notification shows up in the Apps list as "Not installed for this user." (as expected).
We'll see if this fixes the instability I was having. My phone started crashing randomly and then having Notification turned back on when it rebooted. My suspicion is that the malware was causing the crashing, and something about it was letting it turn back on. Hopefully, this use of adb to uninstall it for user 0 will fix the problem. May take a few days to be sure --- it only crashes that often, and my disabling of Notification held until it crashed. I hope that there's no BLU-supplied malware that will 'reinstall for user' at any point. Even so, with this latest stunt BLU has earned my never ending scorn, and I will be replacing the phone soon regardless (I was thinking about a pixel, though perhaps not a refurbished one from amazon).