You are confusing output nodes with input parameters. It's a common error. e..g searchResult.item.sellingStatus.sellingState/EndedWithSales is part of the response (output section), not part of the request (input section). The result of this is that you are in effect making up parameters the API doesn't expect and they are being ignored. itemFilters are mentioned at the top of the docs. SoldItemsOnly is the item filter that corresponds to the =EndedWithSales option.
http://developer.ebay.com/DevZone/finding/CallRef/types/ItemFilterType.html On any doc page, go to the Samples, URL Format section near the bottom to see an example of a URL request. Then add/change parameters from the Input section of the docs, which also includes itemFIlters.