1/ You need to disable the synchronization of the content in your module displaying the listing of categories. Otherwise, the module will try to display the subcategories of the category you just clicked on and if you don't have any subcategories in the category you just clicked on, it won't show anything.
2/ You just need to edit the CSS of HikaShop ( in the configuration, under the tab display ). Then remove the CSS code
.hikashop_checkout_address_left_part{
width:350px;
float:left;
}
.hikashop_checkout_address_right_part{
width:350px;
float:left;
}
and the address views will be displayed one below the other.