Forget about that 9800 lb tow capacity. You will run out of payload, long before you get to that. That 9800 tow capacity is, with a 150 lb driver, who is alone, and has no cargo. Adding weight with passengers, heavier driver, or cargo, reduces tow capacity and available payload.
What you need to look at, is your payload sufficient to carry the weight of your family, 100 lbs of WD hitch, any cargo you plan to put in the truck bed, and the tongue weight from that trailer. Your loading capacity should be on a sticker on your drivers door post. That is your capacity for everything and everybody you put in or on the truck, combined.
The trailer has a gross weight around 7000 lbs. Loaded for camping, it will weigh between 6400 and 7000 lbs. Average tongue weight is 12 - 13% of loaded trailer weight. You're probably looking at 768 to 910 lbs of tongue weight. Plus the weight of the WD hitch.
Ask the seller about actual loaded weights on the trailer. You want to know loaded tongue weight and loaded trailer weight.
Adding helper springs or airbags, may help with the ride, but, nothing will increase payload and GVWR.