You're towing with basically the same truck I have. My trailer brake gain is set to 6.5. I had a problem when we first got the trailer in that the brakes didn't seem to be engaging properly. This was due to an adjustment issue that when adjusted properly, worked great.
I did have a bit of a scare (fortunately on a relatively flat road) with a "check trailer wiring" message. The connector had vibrated out a little from the in-bed connector. The truck was still able to handle the additional weight but it's not something I want to do every day.
Al & Linda
2022 GMC Denali 3500HD SRW, Crew Cab, Std bed, 6.6L Duramax, Allisons, PullRite Superglide, Triglide
2011 Crossroads Seville VF35CK11 (sold)
2021 Alliance Paradigm 365RD