Pardon me if I am misunderstanding (and for repeating myself), but are you trying to put the #4 bolts in before or after attaching the bracket to the engine? I think you are trying to put the bolts in after attaching the bracket to the car, and I think it should be done before attaching the bracket to the car. Forgive me if I'm wrong, but which way are you doing it?
With regard to the stretch belt, the "by the book" approach utilizes a special tool which is pricey. Others, though, have made it work with a combination of techniques.
Here is one link with a thorough description, and here is
a YouTube video with another option (the video is on 335d but it is of course an M57 engine).
Stephen