It sounds like you may have a few different issues going on with your Chevy 3500.
It's possible that the issues with your trailer wiring are related to the brake control module problem, but it's also possible that they are separate issues. I would recommend taking your truck to a certified mechanic or dealership for a more thorough diagnosis. They can use diagnostic tools to check for codes and perform a more in-depth diagnosis of the electrical system.
https://dtcvehicles.com/c0800-code-device-power-1-circuit-malfunction/
It sounds like you may have a few different issues going on with your Chevy 3500. It's possible that the issues with your trailer wiring are related to the brake control module problem, but it's also possible that they are separate issues. I would recommend taking your truck to a certified mechanic or dealership for a more thorough diagnosis. They can use diagnostic tools to check for codes and perform a more in-depth diagnosis of the electrical system. https://dtcvehicles.com/c0800-code-device-power-1-circuit-malfunction/