Hello,
We have checked widgets with Storefront theme –
http://prntscr.com/r7hg2b – filter by rating & filter by price are default WC widgets >
but there is no filter by price on the frontend – https://prnt.sc/r7i4bl It means that the problem with price filtering is independent of the theme. Our own filter by price exists but works not good, as was mentioned by you, but it is not a theme bug, in your case.
About sorting – http://prntscr.com/r7hjp8 – low to high sorting is also broken with Storefront theme.
You can contact woocommerce plugin support with this question. Our theme technicians don’t see any issues from XStore theme and Core plugin sides and we think that the problem started while importing variable products into the database.
Regards