Re the 30% cut - it's a lot, although we know retail took a bigger cut, but let's consider what you get for your money. First up, you get some pretty expensive infrastructure to deliver the files to the user. That shit costs money. Lots of it. Second, you get all that community stuff - chat, matchmaking, workshop for handling mods, etc. Third, you can sell your keys anywhere and Steam takes a 0% cut - they basically provide infrastructure for you to then cut them out of the loop. Fourth, they have a HUGE number of customers viewing their store. Getting on there isn't quite the money-printer it was back in the day for smaller games, but for most games it's the place to be.
70% of the money from a huge audience is always going to be better than 90% or whatever it is from a small audience, and I'd be very surprised if the Epic audience wasn't very very small at this point.