At this point, it might be worth either bringing it to your local Best Buy (if applicable) and asking the Samsung Experience rep to look at it, or calling 800-SAMSUNG and seeing if one of the reps there can help.
UPD:
Sounds and notifications > Notifications on lock screen - select "Do not show notifications".
Sounds and notifications > Notification access - Turn Off access for Clean Master and CM Security.
That worked for me. Maybe this is not very wise for the security point of view... but right now it doesn't matter )