As Par said, the treats can work wonders. We had a little trouble introducing Kito and Abbey--we muzzled Kito (he's our alpha), and it was ok, and the first night, we just kept giving him treats when he didn't bark at her, or anything questionable. We had to get even more treats when Riley came to live with us.
I know you aren't "planning" on keeping Bruce, but it just may ease your mind a little more while he is staying there.
I'm keeping you and all of the furkids in my prayers, I hope something works out.
