1) Is there some reason you decided to compile ffmpeg rather than point to a repository and download a precompiled binary?
When I started testing this the version of ffmpeg in the repo for Rasbian didn't include the x264 encoder that's required to send a stream to YouTube. I haven't checked to see if that's changed, but it's only been a couple of months.
2) I like your approach except for the Youtube part of it. I think I'd be more comfortable pointing an RTMP stream to the church's broadcast service. I'm assuming that the Raspberry Pi + ffmpeg solulution can be used to push an RTMP stream to a church-scheduled broadcast URL instead of flv stream to a YouTube URL, correct? Since the zillion ffmpeg command line options can be a bit intimidating, I'm wondering if you could break down what they all do and maybe include the option syntax for an RTMP stream URL?
One of the reasons I went with YouTube was because I had a hard time with the church's system always complaining about me not sending data fast enough (I was testing from home, on a quad-core i7 and a gig fiber internet connection...), however this was before they added the high bandwidth switch, so maybe that will make a difference. You should be able to take the same command just replace <server URL>/<Stream Key> with the string provided by the church broadcast system.
I can try and breakdown the command line options from my github post, but I'll post it over there.
Have you found that the "Record Out" level is high enough? I've got a couple of buildings with older sound systems in them, and the "Record Out" levels aren't adjustable and possibly too low. I'd rather not have to add an amplifier into the audio path, so I'm wondering if there's any broadcast volume adjustability in your solution? I see an ffmpeg switch in your example that says, "volume=20dB", so it seems possible.
The "Record Out" is a live level output, it should be able to drive a line level input. Most of your broadcast software, or your OS should have the ability to gain the line level input if you need to "turn up" the volume on it a little bit. In the case of ffmpef yes "volume=20dB" accomplishes that.