I figured out one way to make it work. I created an action method in the Product controller that takes the video Id as a string parameter.
Then I call the view and pass my id as the model.
Another problem I found was that the MagnificPopup script had a type property set to image and that did not let my iframe display, I simply changed the type to iframe and styled it to fit. Evidently the iframe type has no problem displaying images also.
Here is the updated code for the thumbnail image:
<a class="thumb-popup-link" href="@Url.Action("spin", "Product", new { SpinVideoId = @Model.SpinVideoId })" title="Product 360 Image">
<img src="~/Content/Images/360img.jpg" alt="Product 360 Image" title="Product 360 Image" />
</a>
I hope this helps others!