How thick of a layer of food were you adding? Mine does get warm but not hot.
On the lid is a chicken wire mesh not a screen. But even with a screen then BSF would lay there eggs on the top and side of the lid and the larvae would find their ways in. The only thing that helps a bit is a BSF bin nearby
I would feed a very thin layer on top but it would always get super hot even when it was in the 20's outside. I had to pocket feed just one section of the four but it would still build up good heat. Now that I precompost my greens it stays cooler then the outside does. Really like your CFT build though. I am going to start a few custom built ones to fit certain spaces I have available.