Right now, with that 1/2 ton Surburban, you don't have enough truck for the 7,000lbs you are towing. So, stay in the flat lands.
When you decide to go across country, and you tow your present trailer, you will need at least a 3/4 ton truck. If you up the size of the trailer you need to think 1 ton.
If it's mountains you will travel, you should consider getting an exhaust brake regardless of the size of the truck or trailer. I drove mountains out west for 3 yrs before adding an exhaust brake and still wish to god I had gotten it right away.
Approaching a mountain grade I always dropped my speed to 35-45mph as I approached the downgrade. I do not let the speed exceed 50mph on the way down. This is for grades from 5 to 7% in decent. When the speed reaches 50-55mph, I hit the brakes hard until it drops back to 40-45 and then let it climb again and repeat as you descend. If you ride the brake, you will smoke em and crystalize the brake pad which renders them useless and will need to be changed asap.