Really good job on launching your store. I think there isn't a ton to change, but I'm going to nitpick anyways, because there is always room for improvement :D.
After looking I couldn't find a sense of urgency. Imagine you are a customer browsing an online store. Maybe you are ready to buy maybe you aren't. But there is a good chance you aren't in the buying mood at the moment. If you add a sense of urgency to your store it can help more of your customers to buy, and have them buy faster. One way you can do so is by adding https://apps.shopify.com/better-countdown .
An important thing I couldn't find is reviews. Adding reviews would help your customers research the products they are going to buy. Plus if someone likes a product they bought from you they can leave a review.
Nice job on your all of your hard work so far, and I'm sure that just a few minor changes will really help.
P.S. I created an email course at https://mailchi.mp/7d8692283c12/shopify-conversion-course, after reviewing a bunch of stores I noticed that there are a few tips that might help, and I created an email list to help with it.
To learn more visit https://www.answrly.com/
$300 on Facebook ads is not a lot. Your product is not impulse item and people coming to your site could still be in research mode. With that said,
even with a good CTR or tons of traffic, if people are not buying then it's not the right traffic. Not all traffic is created equal. The one thing we tell each client is that you can get traffic of all kinds but that does not mean it's the right traffic for your store. Here are some ways to make your store even better and make people want to purchase.
Product Page Feedback
Your store just needs some tweaks to take it up a level. Hope you found this helpful, if so please click "like" below to let me know.