Couple of options here. First look inside your door for this sticker.
You want where it says "occupants and cargo should not exceed x lbs". This is your payload before hitch, passengers, gear and pets etc. Subtract the weight of all passengers, pets, gear in the truck plus about 150 lbs for the actual fiver hitch. What is left is what you have available for loaded pin weight. Typical pin weight is around 20-25% for most rivers, I'm not certain if this Target range changes for toy haulers based upon the garage contents.
The other more precise option is to go to the truck (or local dump or feed store) close to you and weigh your truck with all occupants, pets, gear etc plus full tank of fuel. If at a cat scale
weigh front axle on scale pad 1 and rear axle on scale pad 2. Cost is typically $9-13 for first weigh, if you ever need to do a reweigh in a 24 hrs period, then the reweigh would be around $1-4.
The ticket will now give you individual axle weights and a total truck weight. Take the truck rear axle weight and subtract it from the truck rear GAWR. This will give you the amount of pin weight your axle can handle. Take the total truck scaled weight and subtract it from truck gcwr to get your adjusted tow capacity. The loaded TH weight must be less than this. Take the truck scaled weight and subtract it from the truck gvwr to get your available payload. The loaded pin weight will also need to be less than this number.
You will find you can haul much less trailer than you initially thought. But staying within these ratings will give you a safer and more comfortable towing experience.