It is fire resistant. Can the ceiling withstand the weight?
yes, will work fine, what span do you have between the joists that you will be attaching this to? 5/8 is good for up to 24 spans.
The difference is 1/8 of an inch, and both have a fire rating, but 5/8' has a better rating.
It would depend on the length and width of the room. But most likely yes. I've seen some rooms (actually garages) 60ft long by 20ft wide put on the ceiling. 2X4's would hold pretty well if it's not a huge area, other wise it might sage. Anything larger will definitely hold. Just as long as it's secured according to manufactures directions. But it should hold.
Most anywhere will support the weight. I remodeled my heater room in all 5/8 rock.
