Yeah, that's the long standing 'fanon' -- that the weapons and ships that were 'new' to players in WC2 had to be entirely new technologies. We know years later that that wasn't true, as more extensive backgrounds for things like Broadswords, torpedoes, anti-matter guns and particle cannons were established. The Ralari, Fralthi and Concordia-class ships seen in the movie all mount Anti-Matter Guns -- so the weapon must have been around in 2654.
Yes, I'm sure. The Confederation Handbook, p.25: "Duel-Pulse Rotary Barrel Neutron Gun (forward)".
The Rapiers are entirely unrelated -- the ship in the movie is the aging CF-117 Rapier... the ship in the game, introduced later, is the F-44 Rapier II. The Roman numeral designates an entirely new spaceframe -- like how the P-47 Thunderbolt and the A-10 Thunderbolt II are unrelated in real life.
They were antimatter torpedoes. From the Handbook again: "In 2648 all in-service Broadswords were upgraded to mount two antimatter torpedoes...". The 'antimatter' in 'antimatter torpedo' describes its warhead, not its locking mechanism.