I am trying to create a world map in Robinson projection (ESRI:54030) from the Wikimedia World Map, using QGIS Map Composer. It should have a grid (spacing about 20°, not too bold/aggressive) and a zebra-style coordinate frame and look approximately like this (regarding number and boldness of lines and rounded sides):
You see: The coordinates at the frame are nonsense, the corners are not rounded, and the grid lines are hard-coded to 5cm or so, as "Map unit" didn't work. I'd rather have the grid lines follow the meridians and circles of latitude with something like a 20, 40 or 60° spacing. Also, the grid lines seem too bold. But my biggest concern is that the frame doesn't fit to the map but rather leave plenty of margins around the actual map. And though trying many different things, I have not yet found a way to have the actual map fill the map area completely.
Could somebody guide me through the composing process or refer to a good tutorial?