1. Simply make the callout point "to space" and not be locked onto the part. Unfortunately, then you cannot use the properties of the part for the callout text.
2. Double-click on the detail view to "go into it". Then add the callout in there. The restriction here is the detail view perimeter ... the callout text box/circle cannot go outside the detail view area.
Jon Balgley Autodesk Configurator 360 / Inventor ETO team Autodesk, Inc.