Add upsell to shopify page

Looking to add this upsell to a product: https://www.loom.com/share/97c35f61477843008cc176af01fbc73a Where they get free shipping if they add it on. I tried adding it but it wasn't working and randomly kept messing up the add to carts. Also want to clean up the design where it looks more professional. So it has a percentage off on the right side of the add-on plus puts the pricing on the button. See here: https://drive.google.com/drive/folders/13AK8pl5D8Ieo9UkFdc5ShGw9wM9011Xq?usp=sharing https://littlewandererbooks.com/ Some of the copy ai suggested: https://docs.google.com/document/d/1gnYVeaizfmhdBJ9RdT3frMQstBTUKgI_Z7YdmIfaxzU/edit?usp=sharing But i would like what you think is best to do based on experience.