[spoiler] um...Could we not just have come back for him?

[cantremember]

Also she broke mid-sentence, my understanding of it is also that she didn't commit suicide, but the hardware malfunctioned, perhaps due to the ocean pressure.

Simon-3 could accept it more easily after being copied, because he wasn't the one being left to die, he was being selfish and the reality only struck him after HE would have to be left behind after launching the Ark.
I think he believed he would be the lucky one and his copy would just have to deal with the consequences.