Yep, what they said. Get a better self-defense piece. There are plenty of good, used double-action revolvers out there that would be much better and not finacially prohibitive, usually.
You might also check with your local sheriff and see if they hold any auctions. A friend's father has bought several things at police auctions on the cheap, including an M1 Garand for $250. I'm sure you can find a good defensive pistol at one for fairly cheap.
In the mean time, you might consider slugs in your Contender, assuming you can hit anything with them. They'll probably be about .45 Colt Cowboy Action level in effectiveness, I would think, but you'll get better penetration than you will with shot. If you insist on going with shot, I'd go with #4 over #6, but that's just me.