Try to get raw video from that camera, that hex translated to ASCII is GRYB so it might be uncompressed or not.

Yes, should be resolved.

I wrote demuxer for dav files, feel free to test it.

Can you explain in detail?

Should be fixed.

Use -max_muxing_queue_size 512 before -c copy.

Forever, because there is @pause at end, just press any key.

If you use libavfilter, you can call av_frame_get_buffer()
You first need to allocate AVFrame with function from libavutil and set some parameters in newly allocated AVFrame, as explained in doxy.
The function to allocate AVFrame is av_frame_alloc().

That message is just informal one, and should not have any impact on output.

Ah, the only way is to use aformat=channel_layouts=mono for every input before amerge:
Repeat similar for rest of tracks.