The mysterious small square radiator is your power steering cooler.
In my experience 7000lbs is about the maximum you want to tow with any 1500 series vehicle. The tongue weight of the average 7000lb trailer is right around the 1000lb mark, which is about all the payload capacity the typical 1500 series vehicle has with passengers on board.
It starts to get uncomfortable driving once you pass that threshold. Not unsafe necessarily, but you won't enjoy the trip as much; you'll be more tired and stressed at the end of a day of travel.
Your current trailer has a GVWR of 6950, right? Odds are it doesn't weigh that much fully loaded. Trailers in that size range tend to have a bit more cargo capacity than the typical camping family will utilize.
You should be able to upgrade to a marginally larger trailer and still keep the total loaded weight under 7000lbs. Look at trailers with GVWRs of 7500lbs or less and see what you like.