oh man that was hard to read
I can't imagine finding him like that....my heart goes out to you. I don't know why other dogs seem to pick on smaller ones so often....then again - we hear the bad stories & I know there are far more good stories out there about them being 'friends'. I'm sorry you had a bad 'story'...what a tragedy.
I'm sorry you lost your little Rufus and your husband
has to forgive himself - these things can happen fast and can happen to anyone.