Question

Is there a simple way to select all the nodes above a certain level?

or would the only solution to that be to delete the child elements of that element?

Answer 1

This recursively returns all parent elements of a node:

public static IEnumerable<XElement> Parents(this XObject obj)
{
    XElement e = obj.Parent;
    while (e != null)
    {
        yield return e;
        e = e.Parent;
    }
}

If you want a document that contains only the node and its parents, you need to remove all other nodes though.