I tow my 30FC with a 2014 GMC Sierra HD. Looks like I am in the minority here on two fronts: I set the brake gain to 10. And I use the Tow/Haul mode with the exhaust brake on when towing. They seem to work well together. Our trip last summer was to Santa Fe, then Mesa Verde, then up to middle Colorado, and then back east through Denver, Nebraska, etc. Towing was a pleasure with the Duramax Diesel.
For a hitch lock I use a 5/8 lock from Bolt Lock, keyed to the truck key.
I believe the OP uses a Hensley. I also have a Hensley and after I got the GMC truck as TV, I switched the Hensley bars from 1400 lb bars to 1000 bars.