Yes, FeatureLayer and FeatureService can be confusing, but despite the common first seven letters they are two different things. On the server you can (in 10), publish a map service as a FeatureService (which requires SDE). In the API we have a FeatureLayer which can use any (one) layer from either a MapService or FeatureService. In the viewer, the type="feature" refers to a FeatureLayer and thus can be any (one) layer from either a MapService or a FeatureService.
Note also the difference between a type="dynamic" and a type="feature".
* The dynamic type refers to a full service (behind the scene it is using the ArcGISDynamicMapServiceLayer from the API) and thus its URL should end in "/MapServer".
* The feature type refers to a single layer in a MapService (or FeatureService) (behind the scene it is using the FeatureLayer from the API) and thus its URL should end with a number as in "/MapServer/0".
As for using SimpleInfoWinWidget it only works with single layer, i.e. type="feature".
Hopefully this will help with the understanding of the different types 🙂
As for your initial question, I don't see a "XCoord" field on that layer, try with one of the available fields like "Description", "Category", "Link" etc.