You own the intellectual property (IP) that you create with Spine (same as with Photoshop or any other program). You can sell your Spine project file and the images, video, JSON, and binary data you export from Spine. You own those and can sell them, give them away, or do anything you want with them.
The Spine license and Spine Runtimes license are what define your rights to Spine and the Spine Runtimes.
You do not own Spine. You cannot redistribute Spine or allow others to use your license.
You do not own the Spine Runtimes. If you have a Spine license, you can redistribute the Spine Runtimes, but redistributions must include the Spine Runtimes license.
The Unity Asset Store does not allow you to include the Spine Runtimes license or any other license, therefore you may not redistribute the Spine Runtimes through the Unity Asset Store. You can still sell your IP there, but you cannot include the Spine Runtimes with it.
I believe the Unity Asset Store requires what you are selling to work in Unity. I suggest you make a Unity project that has spritesheets and/or Mecanim to show off your IP. You may also include your Spine project and/or exported JSON and binary data. If people who purchase your IP want to use that with the Spine Runtimes, they will need their own Spine license. We do not have a requirement that you need to include some specific text when you sell your IP, but it is nice to tell people they need a Spine license if they want to use the Spine Runtimes to render the JSON or binary data so they aren't surprised after purchasing your IP.