Shoulder rests etc are a very personal thing and it might be an idea to try several different sorts until you feel comfortable. Every person is a different shape, with different length necks etc, and there is also the big argument over whether to use a shoulder rest at all (though personally I couldn't play without one as I would be definitely dropping it!).
Maybe Liz can help with this, you may be able to try different sorts to see how it suits you. Its a good idea to experiment until you feel comfortable, and you may want to change your chin rest too.
Perlman just pushes a piece of foam under his jacket (and he seems to play OK

), and Anne Sophie-Mutter has no shoulder rest but a very tall chin rest.
If you feel your teacher is pushing you too fast then just talk to him / her, but I would think that your teacher knows what's best for you. However it is always good (and I do this now before starting my practice) to play some long slow bows on open strings and just listen to the tone and concentrate on what my bow is doing. Try looking in a mirror to make sure it is straight and not wavering about on the string (ie keeping it on the same soundpoint).
Oh such a lot to do!!!
Jx