I'm trying to do the same thing that you're doing very nicely - flac stream via icecast, carrying MPX - then later I can just have a raspberry pi at my tx site!!.
If I play your stream on my test setup, I get your RDS on my receiver, I just can't get mine working
Hoping you can offer some advice... how are you feeding audio in and out of stereo tool? Are you using liquid soap? I'm trying to have liquid soap take my non-mix MP3 stream and output as pcm to a named pipe, stereotool then takes this and outputs to another named pipe, which is read backing in by liquid soap and streamed to icecast as ogg/flac.