Hello Bagpuss
It is difficult to give you an accurate answer as we don't have all the information needed to confirm the figures I have some concerns that I will explain starting in Paragraph 3.
The fundamental criteria is the cars stated "Gross Train weight" You will find this is the largest value stamped on the cars data plate. This is an absolute and must under no circumstances be exceeded.
The particular reason for my concern is that Nissan has strong ties with Renault (they share technology and some engines). Unfortunately I don't know if Nissan also share Renault's unconventional method of quoting towing weight capacities.
Most manufactures will quote their cars maximum Braked Trailer weight to be the difference between the cars Gross Train Weight and the cars Gross Vehicle Weight. This means the car can be fully loaded and you instantly know the largest size of trailer you can still tow and be legal.
Some Renault models are quoted differently, and the Braked Trailer Weight is the difference between the Gross Train Weight and the cars Mass In Service weight. This is fine as long as the car has no passengers or luggage. If you add any passengers of luggage to the car then your towed trailer weight limit is reduced by the same amount.
I do not know what the Qashqai's GVW or GTW are, but you will find them both on the cars data plate so you can do the maths.
But if my concern is justified, then its not untypical for a 1500kg MIS car to have a GVW of about 2000Kg which means the biggest trailer you can tow with a fully laden car would be down to about 900Kg
If my concerns are unfounded, then it seems you proposed outfit could be quite well matched for both weight and power available.
Dont forget that good safe towing is not just down to weight ratios, and engine power, but a whole range of factors and the biggest influence is the driver.
Take care.