GMC Troubleshooting Questions? Ask a Mechanic for Answers
I am a GM factory trained technician and have been trained on duramax. I will be happy to assist you with your concern, sorry to hear about the repeat codes diagnosing the dpf system can be very difficult.
You are correct the first step is to reprogram the ecm, there is several updates for the module that helps form the dpf getting plugged again.
86grams of soot mass is way to high. You will need to start with a reprogram and using the scan tool to force the vehicle into a regeneration. After the regeneration the soot mass should be close to 0.
Ensure there is no codes stored for the brake pedal sensor, failing sensors will cause the regeneration system not to run. For the P0299 code clean the mass air flow sensor, check for any charge air leaks and road test the vehicle.