I selected to allow for a product to keep selling when out of stock, but now I can’t figure out how to turn it o
I believe you can turn this off from the backend. So go to products, then click the required product you should find an option. If you have variants of the product then click the desired variant, it will open a new product popup there you will find the option to put it off by clicking the checkbox
@InlandGrove 
We run into this quite often with merchants using our Preorder & Back in stock alerts app - STOQ - as we rely on that setting!
- If your product has no variants, scroll down to the ‘Inventory’ section. Here, you’ll see ‘Continue selling when out of stock’. Uncheck and save.
- If your product has variants, click on any of them in the 'Variant’s section. You’ll find the setting in the same ‘Inventory’ section for that variant.
You can also change this in bulk on the ‘Products’ page of admin by selecting a few products and then clicking ‘Bulk edit’. 
Got some quick screenshots for you in the attachments but let me know if you need any help here!
