Hello,
1) Go to Theme Options > Styling > change active color from white to something else because all that buttons use active color.
2) Follow documentation http://xstore.helpscoutdocs.com/article/47-static-blocks
3) Min width that is recommended for source images are 600px. Don’t use too big images because they may slow down your site (for example is 1 image is 1 MB because it is 2500x2500px). So find optimal size for you. Also, we would recommend to use all the images with identical proportion to have nice grid on the shop page.
To set correct settings in WooCommerce > Settings > Products > Display > Images size read this post https://docs.woocommerce.com/document/fixing-blurry-product-images/
Regards