Another (?) which-frame-size-to-choose post
From your description, you're a little taller than me with a little longer inseam and shorter torso.  I'm usually comfortable on both a 56 and a 58.  I fall somewhere between the sizes.  For gravel riding, I would probably err to the shorter bike just to have a little more control.  For pure road riding, I'd probably err to the taller one for better lumbar stretch(if you're in the more-flexible camp).  Fitting is such a personal thing, it's almost something best seen in person, or tried and felt.

Does the shop there have any road bikes in those sizes that you can test ride just to get a feel for it?