Could you fix those quotes? Hard to tell why you're trying to argue now.
1) How would they know to? By the time they figure that out (because it isn't really intuitive), they're already dead. You can't just assume that the Shivans know
exactly how to counter the Flood at every turn without having ever encountered them.
2) Once again, you obviously haven't read any background info on Halo. I'll spell it out. Halo ships operate at speeds in excess of thousands of kilometers per second. Their weapons ranges are measured in thousands of kilometers for the short range weapons. They are, quite simply, completely superior in every single way to FreeSpace ships, which are horribly slow, have butchered ranges, and are ridiculously underdefended. The Halo ship will be out of range in fractions of a second, and will retain range on the Sathanas instead for several minutes, and jump drives have to recharge.
3) Go read the poems again. They are clearly written in a more lofty language than is necessary, indicating hyperbole. Plus, they describe their empire as enormous before they discover subspace. Unless the Ancients lived for thousands of years a piece, they would still not have a substantial (by subspace terms) presense in terms of colonies and expanse. It's impractical to think that the Ancients conquered entire galaxies when, as far as canon is concerned, we have no indication that subspace can be used to reach other galaxies. Extra-solar travel is restricted to jump nodes.
5) We also have absolutely zero hard data on the number of Shivan ships present during the fall of the Ancients. Once again, hyperbole runs rampant throughout your source. There are absolutely zero canonical guesses even at Shivan fleet strength. We do, however, have a canon example for the Flood. Over
four million ships. We also don't have any data, not any
hard data that the Ancients empire was larger than, or even as large as, the GTVA. Speculate all you want, but there is nothing to indicate one way or the other. On that point, all that would be required to destroy the Ancients is a Lucifer class destroyer. One. They couldn't touch it. It could kill their people and planets. There is no correlation between the fall of the Ancients' Empire and the number of ships the Shivans possess. Absolutely none.
6) Anti-stellar weaponry? How do we know what the Shivans used to destroy Capella was a weapon? Prove that first (except you can't. It's a theory). Then prove the Shivans have the capability to do so again, to any star they choose. Then prove that
every single Flood ship would be destroyed in the resultant supernova. It only takes one.
7) See arguments above. Flowery, hyberbolic language. He can and did point blank state that. And he's right.
EDIT: And now that I'm
five six posts behind (
) I'll just hope this makes sense anyway.