While I believe de-clawing a cat is not the nicest thing to do, in some cases it might be better for the cats. It will all depend on the circumstances.
At any rate, I don't think you can work with one cat if the other one's territorial. It's just not in their nature to get along with another rival. It's probably better to separate the felines if they don't get along with one another.
SD, I do believe you should have brought Tigger with you when you were thinking of getting Angel. Should have observed them both when they're put in the same room.
At any rate, I believe the SPCA will try their best to find a home for the cat. If you're hesistant about this, they can put information out there for Angel as she waits for a place to stay with you.