As far as the dialogue goes, here's how I feel it should be written. Others may have oposing opinions, but this is my advice.

Original:

He said while walking other to the man, “what is it marine”. “Sir we have a large anomaly approaching one of the drones near Pluto.”

“Bring it on the screen”, “Aye sir”
Lord price looks at the screen trying to figure what could be so large, move so quickly and be undetected until now. A look of horror appears on his face, he bellows “Get all battle stations onto red alert load up the MAC cannons get all available ships to form a defensive perimeter around the orbital stations.
“Sir Ground forces are mobilised, but may I ask what are we preparing for” asks a marine.
“A Covenant invasion” says lord Price, all personnel within the observation deck had horror and fear on there faces, marines started running through hall ways and securing reactor rooms and docking bays.

The Admiral moved urgently to the display. “What is it marine?”

The soldier looked up, a confused and panicked look on his face. “Sir, we have an anomaly approaching one of the drones near Pluto. It has a large signature similar to a Covenant CCS Cruiser.”

This was bad news. The UNSC's Sangheili allies no longer used the Covenant ships, having altered them to fit the alien's society and customs. “Bring it on the screen,” The Admiral ordered.

“Aye sir”

Admiral Price looks at the screen. Soon the ship was confirmed as a Covenant cruiser, and was on a projected course for Earth. “Alert UNSC outpost 38 on Io, have them prep for incoming Brute forces," Price ordered. "Prepare all available ships to plot a course to Io, and have them give our boys some help."

“Sir," the Marine asked, "Should we prep our home defense as well?

“Not just yet, son,” Lord Price, said, "The Brutes are still too far off for us to greet them yet, but we'll be ready if anything gets past Io."

**It should be noted that Lord Hood (who I assume was the inspiration for Lord Price) was not the "Top #1 Admiral of the UNSC." There were more than one Admirals, just as it is today. His title of Lord is most likely ceremonial, as he was a member of British nobility. It does not mean that he was above other Admirals.

As far as the "precognitive tense" goes, most FF's and stories that I've read are written in either past tense (The Marine fired at the Brute,) Present tense, (the Marine was busy firing at the Brute) or First Person (I fired at the Brute attacking me.) I've never read anything in a "future tense" (The Marine fires at the Brute) unless it was a stage direction in a play.

As far as the Cairo goes, it's very unlikely that it would be operational. The last time we see it, it's near destruction. I severely doubt that it would be up and running as a major hub for UNSC intel.