Six weeks post rhinoplasty and significant increase in bridge width. Is this mostly swelling or a bad result?

It does appear from the photos submitted that you do have very thin nasal skin.  6 weeks after rhinoplasty there is still considerable swelling of the nose.  At this point it is best to be patient and follow the advise of your surgeon.  The frontal view takes time to evolve and the results are far from instant.  

Though still very early in healing phase you do not appear much different. Did ask for a conservative rhinoplasty.

Without feeling the tissue, it's hard for me to say what is swelling and what isn't.  That being said, you have two things going in your favor.  1) its still very early on in the process.  The nose is in the central part of the face with just about most major muscles of facial expression attaching to it in some way or another.  For things to heal fast, we want immobility.  That is simply not possible with the nose as every time you smile, laugh, talk, eat or drink the muscles will tug and pull slightly on your nose.  So it can take quite some time for swelling to come down (up to a few months).  2) Your surgeon noted thin skin and having to graft the tip as well as elsewhere.  All these maneuvers will aggregate to create more swelling in certain patients.  If your surgeon notes that you still have quite a bit of swelling, then give it time.  He will guide you through the healing process.  If swelling doesn't continue to go down make sure you see him as he may be able to inject the nose with corticosteroids if needed to help bring the swelling down appropriately and ensure you do not develop any scar tissue.  Best of luck!