Use Pair Up, seriously. It's nearly game-breakingly good. Well, it IS game-breakingly good on Normal, but you're playing on Hard. Also, if this is your first Fire Emblem, you might not want to do that. These games have a reputation, and even though Awakening is kind of easy for a Fire Emblem game, it's still a Fire Emblem game.
Put a weaker unit in a pair with Frederick to see what all the hubbub is about. Weak unit in front, Frederick in the back. That's the basic power of Pair Up with a promoted character. You do lose an action per turn, but you get characters that are much more powerful on the enemy's turn in return for that. And a lot of Fire Emblem is played in the Enemy Phase.
As for good weapons, you want a few, but Iron weapons are going to see use well into the final parts of the game. They're dirt cheap at that point and can be used a lot before breaking. Awesome weapons are usually a bit fragile.
Also, build up as many supports as you can. There is no max limit on supports in this game, and they stack. The only limit is that you can only have one S rank per character.