The weapons are too similar for it to be a coincidence. They both have relatively weak single-shot modes. They both can be charged and their charged shot uses more ammo than their single-shot mode. The charged shot is also significantly stronger than the single-shot.
Actually, none of the Covenant weapons use hardlight. The energy sword is plasma encased in a shield. The jackal shields are just shields. The beam rifle fires some kind of projectile. the covenant weapons are similar to promethean ones because covenant created almost all of their technologies by reverse-engineering forerunner technology.
Bumping your 360 while you're playing a game on it will ruin the disk. I don't think that there's anyway to repair it. If you can download Halo 4 to your Xbox from a friend's disk, it might work with your disk. If that doesn't work, you'll have to replace the disk.
Actually, the first game to have a difficulty curve was Space Invaders. The game had lagging issues, but those went away as you destroyed more spaceships, so the spaceships would move faster as you destroyed more of them.