Hi Ben, your post is not making much sense to me so let’s clarify a few points first.
Which sensor are you using? The Smartthings multipurpose sensor is the sensor you would usually mount on a door. It works with a magnet. If there is a slight movement but the magnet is still in range of the sensor you will get a message something like, “Kitchen Door Sensor Is Active.” You will not get an intrusion alert . When the magnet gets out og range of the magnet SHM will trigger an event and give you an intrusion alert.
Smartthings Motion Detector detects movement by picking up on small changes in heat, (not exactly technically accurate but accurate enough for this discussion). They can be placed anywhere as long as the front of the sensor has no obstacles in front of it.
At this point I know of now way to change or capture the sensitivity of the multipurpose sensor. Battery life varies among sensors tremendously depending on many factors. My kitchen and front door sensors have the batteries die a lot quicker than sensors on doors that are rarely opened. Also the temperature readings that you see in your app are not necessarily accurate. If you are getting inaccurate readings go ahead and replace the battery first to see if this fixes your problem. Just before the batteries in my multipurpose sensors would die, I would start getting false acceleration readings if this is what you are referring to.