why couldn't he have used it at the beginning and saved all this suffering?
Better yet (as you see it) all Jehovah had to do was to kill his traitor son at the begining (that no doubt he had loved and entrusted with the future of the human race) - But DD ain't running things, Jehovah is, and He knows how and when and why to use his Holy Spirit. In the meantime, it is like being challenged to play chess, you can shoot and kill or silence or ban your opponent but the challenge would still remain: 'You are no good!' (seems that way now doesn't it? -that God is bad!) until shown otherwise.
You must allow your opponent to prove his case and defeat him at his own game. Killing an opponent "at the beginning" only shows that you are more powerful than he is but does not answer his question or challenge that requires justice.
'You you are no good.' As you see it DD, what would you do better?