Hi,
The PRICE_ENDING_0 translation key doesn't exist by default.
But the code in HikaShop looks for it. And if it finds it, it uses it.
So you need to add that translation override line in the override file of your language (you can do so by editing your language under the Languages tab of the HikaShop configuration and then adding the line on the right side textarea before saving).
For the br tags, I don't have it on my end too. It might be added in a view override of product / listing_price so you can check that via the menu Display>Views.
However, you can easily disable the br tags there with that CSS:
.hikashop_product_several_prices br { display: none; }