Trying to display data from a few linked tables in a single popup

Can someone point me in the right direction here please?

I have users who own venues/outlets through which they sell items. So far users can successfully log in and see their own venues/outlets in a repeating group and, using buttons at the end of the row, they can view, edit and delete venues. That all works fine. I’m now trying to add a button that enables them to see in a popup all the products they sell via that venue/outlet and where they can add, edit and delete items. So, I have a datatypes for Products, Venues and Users and one called ProductsAtVenues that records “which venue sells what products” in which I have fields for;
ProductVenueID to uniquely identify each ProductAtVenues listing
Owner (link to Users data type and displayed as UserEmailAddress,
Venue (link to Venues data type that also contains VenueName, Address, etc)
Products (link to Products data type that contains ProductName, Category, Size etc) plus fields for
Date to show when that item was added
Price to show how much they charge for that item at that venue/outlet.

My RG successfully displays each Venue/Outlet that the current user owns. At the end of each row I have an icon to click to display a popup in which I want to show, for the Venue/Outlet on the selected row;
ProductName (from Products datatype), Price (from the ProductsAtVenues data type) that shows the price being charged for that product at that venue and then the Date (from the ProductsAtVenues data type) to show the date it was added.
Try as I might, I can’t get any data displayed in the PopUp. I’m getting bogged down and confused with DataTypes and SearchFor and InitialData and DataToDisplay on the Workflow attached to the button. Is there an example of this anywhere someone can point me to or can anyone offer me a solution? I’d be so grateful if you can.

Many thanks in advance.