I’m glad to hear that you got it working. As for the digest working with rbe, just replying to the email isn’t possible because the system wouldn’t know which topic/reply the email was intended for.
However, I did do some custom work to have the RBE reply-to address added as a tag to the digest. It sounds it’s time to merge that onto the main RBE plugin.
I’ll work on it and have it released by the end of the week.