Almost always light weight kiter has more strength compared to his body weight than a heavy weight one.
Yeah, that one is very important. But on a power delivery from the kite perspective, nothing really changes compared to a light rider. You ride a X-% bigger kite, you get X-% more pull (ignoring net l/d/weight differences between a small and big kite, those kind of even out in the end). Board speed, apparent wind direction and speed, increase in apparent windspeed when edging, all the same.
So you have to get the technique just right, or ride a kite that's better suited for unhooking. Or work on those muscles or that weight. Friend of mine has weighed above 100kg, didn't have problems unhooking. But he's a strong guy.
Ah yeah... My fitness pal app... Really great... For losing weight.. but pay for a personal trainer if you can afford it.. a great investment.. they will help motivate you when your brain weakens to the point of I am over this...