I now solved my issue (3) by setting all relevant property values to null in the "edit" event of the grid. Apparently specifying default null values via the html helper is not honored, so one has to set those manually.
By the way: I learned that my issues here are related to all nullable types and are not specific to enums.
Remaining issue: The filters still show the [object Object] entry. Is there an option (like ValuePrimitive(true) for the DropDownList) to let the grid know that it is using a primitive data type for a column?
Feature request:
In a nice world the grid itself could and would inspect the given model type (i.e. via Html.Kendo().Grid<Person>()) and weave the necessary settings for nullable property types. Any plans to automate this for us?
Best regards,
Kasimier Buchcik