Royal Dutch Shell plc (NYSE: RDS-B) has a fat yield of around 6.7%. But its long-term debt load has increased by more than 50% in the past year and by nearly 120% since the end of 2014. The oil and natural gas giant is now selling assets to get its stressed balance sheet under control. Although I’m fairly confident it will be able to save its dividend, investors should always question their assumptions. Here’s my attempt to do just that.