As far as the trade is concerned, I don't think this would help you. Buehrle isn't enough for a sure thing to justify trading Pedro, Anderson is a downgrade, and your outfield is more than stacked without Edmonds.
The real area where you can improve is by changing your pitching strategy. Your league doesn't set a limit on games pitched or innings, and gives you a fairly substantial 2 points per inning pitched. Having a solid pitching strategy under these rules will be even mor eimportant than in other leagues.
Let's do some quick calculations: Mariano Rivera, one of the top closers, would give you around 226 points if he repeats last year's excellent stats. Garrett Stephenson, nobody's top choice for the Cy Young, would give you 462 (or so - I'm rounding here), or more than twice Rivera's score. Still, I'll wager Rivera was picked a lot earlier than Stephenson in your draft...
Therefore, Gagne and Percival have to go. I probably wouldn't drop them, though, since their perceived value is likely high. Trade them, see if you can get an upgrade somewhere else, and hope your opponents start them often...
You'll now have two extra slots. The best way to go here, if your league plays weekly games, would be to devote these slots to rotating pitchers: pick up free agents who look decent and have two starts that week, and slip them into your starting lineup. If your games are shorter, I'd still pick up at least one starter (a 2b-ss would be perfect for the second available slot) who will give you workhorse numbers: a knuckleballer like Wakefield who will
eat up innings might work well.
Your hitting is already solid, and your pitching staff looks good, too (although the Marlins might cost you some wins). Use your pitchers well and you'll win a lot of games in the very near future. A few minor tweaks along the line, and you'll be in the title hunt, not in the cellar.