How Much Weight Can My 1/2" Drywall Ceiling Take?
You will NOT want to support your 78 1/2 inch rod from the drywall alone. Drywall fastened up to the ceiling is a pretty good challenge just holding up it's own weight then yet you trying to add 70 pounds to that. 

So what you want to do is to locate the support members (usually called ceiling joists) to which the drywall is attached. You would then want to use screws that penetrate through the drywall and and up into the support member to hold up the brackets for your rod. For most ceiling supports the members will be found to be 16 or 24 inches apart so you should be able to find 5 or more support points for the rod if it is running across the direction of the support members. If the rod is running in the same direction as a ceiling support member then you would attach the rod support brackets at 4 to 6 locations along the same support member. In this latter case it means that you cannot locate your bar just any old place but directly under a ceiling support member.  

Finding where the ceiling joists are located can be done with a stud finder tool. A simpler scheme is to get a strong magnet and scan it across the ceiling looking to find the steel nails or screws that are holding up the drywall. Each located screw will be at a point just under a support member. Find multiple points and a ceiling joist map can be created.

If the bar that holds up the ball chain partition is an extruded metal track then the mounting technique will likely not involve any brackets but instead involve drilling holes through the metal track at the correct points where screws can then be run up through the track into the support members in the ceiling.