Hello,
so I finally heard back from the Webflow support. And they have resolved the issue for me. So I’ll leave the response below in case someone else runs into the same problem as I did.
In short, when I purchased my template and then consequently added the CMS plan to my account, the system did not reload my CMS item limit when I added the Hosting plan. I contacted support, and they had to do this for me manually.
So for anyone that gets a message saying you ran out of the number of collections/items on your account, but you know you have purchased more, you must contact support for them to fix this issue. 
Thank you again for pointing me in the right direction.