Hello,
1) There is default space between gallery thumbnails – 10px, frontend – http://prntscr.com/gph19h , backend – http://prntscr.com/gph1ga (xstore/woocommerce/single-product/product-image.php, line 282)
If you see more than 10px very likely your images (product thumbnails) are smaller than item block, for example http://prntscr.com/gph31w that’s why empty space appears. Increase the size of the product thumbnail. In case you want to have very small thumbnails and change the size of the slide item or it’s number then you need to make changes in template files http://prntscr.com/gph5ao according to your needs.
2) Horizontal and vertical sliders – are 2 different types of sliders and requires different parameters. It’s like if bought sedan but thought that you’ll be able to get cabriolet.
We plan to improve theme and implement vertical slider in future but there is no such option in our theme at present and if you want to get it now then additional customization is needed.
Regards