I'm not expecting to get accepted, at least not on the first pass. The audio quality is not that good, but it's as good as I can get it right now. I've put up acoustic foam on some of the larger spaces on the walls, and improvised a sound box lined with foam to put the mike in. This mitigates, but does not eliminate, the echo. I can see little waves on the sound spectrogram spaced at about 8.8 ms, which agrees exactly with the width of the room, 3 meters.
But I've gone through the process once, and I can do it again. I had promised myself that I'd get the demo submitted by the end of the week, because I didn't want to lose momentum or give in to procrastination. And it's done. Five hours to go till candle lighting, and now I can relax a little.