Hey Paulo
Unless anyone speaks up, you may find the members here post in topics mainly discussing ebike interests.
Also, the GoldenMotor staff rarely use the forum... Hence why you may not get much action on this post.
From what I can see on the GM website, the largest wheel with EMB is 10" @ 24v/240RPM
15Km/h is quite fast for a 'wheelchair' - seems to me that you are looking for a mobility scooter type motor. >50Nm locked is pretty hefty
I do doubt the 10" 'scooter' wheel on the site can produce this.
The IM-50B controller will probably suit any brushless DC motor within its specs. So possibly if you are firm on the 16" wheel size, and you like the GoldenMotor controller - perhaps source the motor you need elsewhere and use the controller to move it
Anyways good luck