How does TV bed cargo weight affect tongue weight

I tow with a measly 400# tongue weight, and 1580# payload. We keep a 700# ATV in the box with a few other odds and ends. We are usually around 100% GVW, truck handles it fine. GM trucks tend to wallow a bit more, but that is just a general observation from my last 3 HD GM work vehicles.
With careful loading, a so called half ton can work. With 2000# of payload, I think you will be fine. Personally, keeping under the GAWR's is more of a safety issue than GVWR.