Most HDMI splitters take the "lowest common denominator" of video and audio capability. In short the splitter looks at ALL of the destination devices - the TV, the AVR etc.. - reads the EDID information for all of them and then establishes the signals that are compatible with ALL of those devices (lowest common denominator). The splitter than creates a new EDID to send to the source device (your PS3) that is only that set of common compatible signals. The source device then adjusts the output to match only those signals. Because your AVR is not 3D, frame packed 3D is not included. Even if it would send the frame packed 3D, it is my understanding that the structure of the frame packed signal is different and the location for the lossless audio in that signal is different so you AVR, which is not 3D, could not find the lossless audio any way.
There are some 3D Blu-ray players that have two HDMI outputs for this situation. One output that carries the 3D signal directly to the TV, by-passing the non-3D AVR. The other output that takes the lossless audio (only) and repackages the signal in a more traditional way to send to your AVR. Your PS3 does not do this so you might be limited to using the Optical output from the PS3 – at least for 3D.