Item values and logical ranges at updates

Depends on the binding. I wish ALL bindings supported transforms. Most of the lower level generic bindings support transforms on the Item state (e.g. MQTT, HTTP, Exec, …).

OneWire appears to not support transforms but you could use a transform on the event bus but subscribing to the topic directly on your Item rather than relying on the event bus to update the Item. This will require your Item to have a different name than the remote one but then you can apply a JS transform to test the range of the new state and if it doesn’t make sense return NULL (I think that will work).

This is indeed a limitation. If you need the previous value you will need to use a Rule and proxy Items.

Also look at Design Pattern: Associated Items

There is no such mechanism. The standard approach is to use proxy Items and Rules.