[motorherz]

I've changed all settings as you adviced. My testvideo: "edge of tomorrow". When playing now, my projector tells me, that 1080p/24fp mode is activated. But no audio. Now I left all adviced settings and went back to DESKTOP, the projector shows: 1080i/60sbs and I have audio.
So, here are the messages from "tvservice -s":

when I play the video with the 1080p setting: (no audio)
state 0x12000a [HDMI CEA (32) 3D FP RGB lim 16:9], 1920x1080 @ 23.98Hz, progressive

when I play the video with the DESKTOP setting: (with audio)
state 0x12000a [HDMI CEA (5) 3D SbS RGB lim 16:9], 1920x1080 @ 60.00Hz, interlaced

Don't use DESKTOP. Your scaler is wrong in reporting 1080i as its preferred resolution, so you should override that. Set it to 1080p and framerate to 60.
How does it behave if you enable/disable passthrough? With passthrough disabled any different with number of channels set to 5.1 or 2.0?
Any different with omxplayer enabled/disabled?
How does it behave with "Use Full HD modes for 3D" disabled?

I tested all your advices separateley. In all modes I have no audio. In all modes (except the mode below) the projector shows 1080p/24(FP).

when I enable OMXplayer and disable MMAL player and disable "use full HD modes for 3D", my projector tels me 1080p/50(sbs). This must be true, because the screen size is changed smaller. no audio.

Should I try some other combinations with the setting OMXplayer enabled? What do you need?