If you manually turn on DND, it will be set to "until you turn it off." But I use it on a schedule, and you should be able to set it so that the alarm overrides DND. Go to the DND menu, then tap Schedules (do NOT tap the "Turn on now" button). Then check the Sleeping box, and tap the gear icon next to it. Now you can select which days where DND should automatically turn on, the start and end times, and also if an alarm can override the end time. As long as the schedule is set, it should continue until you turn off the schedule (by unchecking that box). I would agree that this is not the most intuitive setup.
I understand what you mean about the camera shutter lag, but I was wondering if increasing the shutter speed might help. If it doesn't, then see if the same problem occurs in Safe Mode (in case some 3rd party app you installed might be running in the background and causing the system to lag).
https://www.hardreset.info/devices/s...iii/safe-mode/