The projector is a native 1280x800 but will accept a 1080P input (1920x1080) and convert it down. It is better to send a native signal as then the projector is not rendering it to fit.
As for the issue with PS3 and Projector and 3D it could be a few things. Is the projector in automatic 3D mode? Frame Packed is usually not a issue but TB and SBS 3D a lot of times the display needs to be set to SBS or TB as it doesn't sense the format. The PS3 has some setting's in the menu to get it to output 3D in display menu I believe. With the PS3 one can also play with depth by changeing the display size setting, smaller equals more depth larger less depth.