Hi @macgreen23, welcome to the forum (and apologies this seems to have been missed).
There seems to be a misconception here - the telemetry data displayed in Cockpit typically comes from the autopilot, and even if you’re able to trick Cockpit into thinking data you’ve sent directly is in fact from the autopilot (e.g. by using the autopilot’s system and component IDs) that doesn’t provide an immediate pathway for that data to go to the autopilot from there.
You should be able to send DISTANCE_SENSOR MAVLink messages to the autopilot (which should then forward them to a connected control station computer, e.g. running Cockpit), and you can set up rangefinder parameters in the autopilot if you want it to potentially make use of the data for something.
The barometer depth is more complicated, because ordinarily barometers need to be supported via a driver in ArduPilot’s AP_Baro backend. It may be possible to create a custom driver via a Lua script running on the autopilot, but that would require some extra investigation.