Hello,
1) I checked related products and don’t see the problem with the alignment https://prnt.sc/103qund
2) Add the below code to Theme Options > Custom CSS to limit the product image height and height of the gallery images
.product-images .woocommerce-product-gallery img {
max-height: 600px;
width: auto;
}
.product-images .woocommerce-product-gallery .thumbnails-list img {
max-height: 100px;
width: auto;
margin: auto;
}
3) Did you set correct selectors according to docs https://www.8theme.com/documentation/xstore/plugins/woocommerce-infinite-scroll-and-ajax-pagination-settings/
Regards