3. Forerunners traveling in slip space might have survived the halo event (because they were not technically in this universe, but a alternate dimension, which is why the shield worlds worked)and possibly established a colony on earth.

4. The forerunners are in fact dead as was assumed. They fled to the shield worlds, but slip space does not block the halo effect, and so they all died. The only survivors were the ones in the ark, who fled in the only surviving portal: to earth.

Most Sincerely.

Until Harvest was discovered, the centre of the Covenant religion was the dogma, that EVERY member of the covenant( every race) would go on the Great Journey, when Halo would have been discovered and fired (That`s why elites said to fallen comrades:” Although you may die now, you will come with us on the Great Journey, when the time has come!”). This belief was the reason for the stability, the commonwealth and sometimes even harmony of the Covenant. But this dogma seemed to be crushed after they discovered humanity. From what Mendicant Bias told them, the Prophets believed that these “Reclaimers” were Forerunners. So they came to the logical conclusion, that not everybody would undoubtedly go on the Great Journey, that some could be left behind. The first thought of the Prophets then was of course, that this fact would crush the Covenant, which had been held together only by this dogma, there would bee civil war and the race of the prophets would likely not survive this.
So they decided wiping out the humans on harvest to be the first act, so nobody except them could learn the truth. But in the time of these events they also discovered evidence of the existence of the halos and to maintain their religion in the time after this they found a way to merge these two opposite evidences together: In the belief that only the strongest, the merciless would go on the Great Journey. So they really believed that the Gods (the strong and merciless Forerunners) would like to see the destruction of the humans by the hand of strong, worthy believers, because the humans were weak and an abomination of those, who deserved to be called Gods( “Your destruction is the will of the gods, and I am their instrument!”…”They declared humanity to be an abomination to their gods…”). And this gradual, careful shift in the covenant belief dictated by the prophets played an important role in causing the Covenant Civil War in the end( Getting rid of the untrusted Elites, who threatened the prophet`s claimed undisputed throne on the Great Journey( “The Great Journey has begun. And the Brutes, not the Elites shall be the Prophet`s escort!”)). You can hear Truth saying those things all the time in Halo 2 and Halo 3 (“When the Great Journey comes, the weight of your heresy will hold(?) your feet and you shall be left behind!” “Let him be! The Great Journey waits for nobody, brother, not even for you!” “Fight and show no fear! If you fail, then a fate even worse than death awaits you: We will travel on without you!”)

Other than that, I agree with everything.

How ironic.