Hello Chris, welcome to the forum and thanks for your support.
What is your device model?
Your minimum and maximum shutter speed and ISO values are entirely dependent on what your device allows third-party apps to access. This can be very different than what the device native stock camera can access, unfortunately.
I'll also add that the camera preview is limited to 1/5 of a second of shutter speed to avoid queuing. This means that when setting shutter speeds longer than 1/5 of a second, it is not WYSIWYG in the preview. The preview may look dark, but the captured photos will look how they should. I'm not sure if that is the case here or not?
The user guide should be back online now. Sorry about that.