Hello,
As I can see, you are using Elementor, so set the Line-height in global settings of Elementor also – https://elementor.com/help/global-fonts/ About thank you page, check how it works when a default theme is activated. Provide us with screenshots and URL, for example – https://xstore.8theme.com/elementor/checkout/order-received/6511/?key=wc_order_nk5BDEuZ8g8A3
Regards
