The body#skinTemperature stays at NULL, but I think this is to be expected (for ScanWatch2)?
The sleep#sleepSkinTemperature stays at NULL, to be expected for ScanWatch2?
Some minor findings:
You might want to check the sleep_efficiency value, it seems as if OpenHAB receives a float (0..1), but your documentation suggests it should be normalized to percentage (0..100)?
In the MainUI, the footer text for body temperature and skin temperature are probably too technical?