Ending Book value is the one you need for yor purpose - set it to 1000 for your vehicle, and it will not depreciate below this value.
This field is normally hidden, Unhide it, besides, you may have to set Allow Changes in Depr. Fields to Yes in corresponding Depreciation Book card, if Navision cries this field is not editable anymore.
That means it is a FlowField, summary of ever posted salvage entries. sorry, amounts, as special Salvage entries does not exist.