Although you can, our Switchboard system is much better suited.
Yes. Channels can be restreamed the exact same as any live stream. You can send your channels to any service, including Periscope, Youtube, Twitch or Facebook.
Yes. API documentation for the channel system can be found here
Video files should be mp4 container, with h.264 video and AAC audio. Audio files should be m4a (aac), and at least 44.1 Hz.
As many as any other live stream. A channel creates an output stream that behaves exactly the same as any live stream. That live stream gets distributed with our global network of servers, just like a live stream.
SEVU works the same on a chanel as for a live stream. You can read about it here
Yes. You need to configure the Roku channel as a "live stream", since that's what the output of a channel is.
Yes. Setup a switchboard with the live stream as the higher priority item, and the channel as the backup. The live stream will immediately take over when you start sending a stream.
To use a ScaleEngine channel in Instant TV Channel, you'll need to be sure to set the StreamFormat parameter to HLS, and set the Live parameter to true. Make sure you provide them the HLS playback URL.