Wow, this looks quite nice!
Except the frequency stats. Subscribing all topics is a really really bad idea.
The solutions are not straightforward, but generally circle around topic statistics (builtin, but need to be enabled per pub/sub or via a hack), or tracing (ros2_tracing). Recently, Kat mentioned ROS 2 Graph Monitor which uses the first approach with hack. Maybe the two projects could cooperate? Yours as a nice TUI, and Polymath’s as the data source…