The below should help you get started on what/how to determine what you can safely tow
Thanks to Rustic Eagle (Bob) who contibuted info for this post.
The amount of the trailer's weight that presses down on the tow vehicle's hitch ball. Too much tongue weight can cause suspension/drivetrain damage, and can overload the rear of the tow vehicle causing the front suspension to lift to the point where traction, steering response and braking are severely compromised. Too little tongue weight can actually lighten the rear of the vehicle, reducing rear-wheel traction and causing instability which may result in trailer sway or even jackknifing. In some cases proper adjustment of the WDH may be required to correct the effects of the trailer tongue weight on the tow vehicle's hitch ball.
For towing trailers up to 2000 lbs. gross loaded weight (Class I), the maximum tongue load should not exceed 200 lbs. For towing trailers over 2000 lbs., the loaded tongue weight should be 10-15% of the loaded trailer weight.
For fifth-wheel trailers, the loaded tongue weight should be approximately 15%-25% of the loaded trailer weight. Note that the loaded tongue weight can easily exceed a 1/2 ton (F150/C1500) pick-up truck's rear GAWR, and can quickly reach that of a 3/4 ton, and some 1 ton's as well.
To measure the loaded tongue weight, disconnect the loaded "level" trailer with only the tongue jack stand on the scale platform. If the tongue load exceeds the upper weight limit, move more of the trailer contents rearward to achieve the recommended tongue load. If the tongue load is less than the lower limit, shift the load forward. This process is based on confirming that the loaded weight of the trailer doesn't exceed it's GVWR.