I don't know if you realized/still check the forums but the cave is purely flavor (and a single secret that's pointless to people who don't already know a lot about the in-game universe) to make more than one omega kerfus, it is pointless beyond that, there is a radioactive capsule on the map on world-gen. If you're really that determined to get multiple omegas and hate the caves that much just get the capsules from new saves and toss them in the mailbox.