I can't look at your file until later. I wanted to ask if you have used Form New Part to put all the pieces that were sliced into a single part. Once you do that, you will have a connected mesh across all the bodies, with no need for contact being defined in Meshing. By deleting any contacts and having Shared Topology from the single multibody part, you should eliminate all the unnecessary walls and interfaces in Fluent.
Here is an example of using Form New Part and benefit from Shared Topology. See if that helps and reply with your results.