There is nothing wrong with cooking ribs at 280.
As far as why your fire is dying down. Not nearly enough info provided to help us help you.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)