Like you I have one cat that came to be declawed and the other cats will pick on him (one in particular). Unfortunately this cat is deaf, so some of the standard approaches don't work to well. What I have learned, is that like little children, a "time out" works wonders. I pick up the attack cat and isolate him in a small powder room for about 10-15 minutes. When he comes his attention has moved on to something else and the fight is stopped.

I also put a collar with a bell on it to warn the declawed cat that the attack cat is coming. This also gives him time to move away.

I am sorry this is happening to Stitch. It is hard to watch one of our furry ones in that position.