If the trailer has brakes, it sounds like John Deere is saying you can go up to 7000 lbs towing (see below). They would have to be hydraulic surge brakes or you would have to add an electric brake controller.
Even still, I wouldn't plan on going that high with this small tractor on a regular basis. It likely won't be able to pull that much weight up an incline. Adding
ballast will give the tractor more traction, but will not increase its tractive force, so it will be even less capable of pulling the gross combined weight up an incline.
Occasional pulling of something that heavy on level pavement - probably OK. For example, I use my 4100 to move a 5000 lbs boat around the driveway, but I wouldn't expect it to pull it up a launch ramp (or even feel safe backing it down the ramp)!
From the 4110 owners manual:
Towing Loads
CAUTION: Avoid injury! Stopping distance increases with speed and weight of towed load, and on slopes. Towed loads with or without brakes that are too heavy for the machine or are towed too fast can cause loss of control. Consider the weight of the equipment and its load.
Observe these recommended maximum road speeds, or local speed limits which may be lower:
If towed equipment does not have brakes, do not travel more that 32 km/h (20 mph) and do not tow loads more than 1.5 times the tractor weight.
If towed equipment has brakes, do not travel more than 40 km/h (25 mph) and do not tow loads more that 4.5 times the machine weight.
Ensure the load does not exceed the recommended weight ratio. Add ballast to recommended maximum for machine, lighten the load, or get a heavier towing unit. The machine must be heavy and powerful enough with adequate braking power for the towed load. Use additional caution when towing loads under adverse surface conditions, when turning, and on inclines.