Whilst technically you are right in that he says half of all life in the universe, I don’t think he meant all literally as you are interpreting it, but most likely all sentient life. The reason for this is i believe it is implied that Thanos was already trying to enact his plan manually, the example provided was his genocide on Gamora’s home planet and how the results of that act made her planet flourish afterwards, not to mention that we only see half of sentient life disintegrate after he snaps his fingers.
On that snap, although I mentioned the time stone alone having the power to reverse time, hence the likely avenue for our hero’s to return, as Thanos used the gauntlet to make half of life end, I assume it would make sense for the gauntlet with all infinity stones to have the power to turn the universe back to how it was at the snap of a finger as well
My wife asked me why I carry a gun?, I said "Decepticons"... She laughed, I laughed, the toaster laughed, I shot the toaster. It was a good day.