What does "keep the same format" mean?
Do you want the spreads as single pages? Is this going to be printed?
So, what's the problem?
If you export as single pages you can set the view for 2-up in Acrobat. Alternatively you can export as spreads for viewing but you'd still need single pages for printing.
I'd reconsider some of those spreads since the edge of some of the artwork is right on the spine.
The PDF for viewing and the PDF for printing probably need to be exported separately.
Smallest File size is fine for viewing, but will not work well for printing, because it makes the images lower-res.
A side note: on both of your pages, you have overset text (so some of your text is hidden)
You should find and fix all of these before doing your exports
Ok thanks Bob, yes I'd shuffle the art around so the spine doesn't interfere.
Thanks for all your help!
Thanks for your feedback! I'll have another bash at it today