Hello fayiqa,
Well you are right whatever you have mentioned above. The receiver sensitivity parameter is an important factor and you have put it right because it is an average power required for the receiver to respond or show any results. And for your query about putting sensitivity equal to -100 dBm from -30 dBm means that the receiver requires less power to detect a signal because -100 is more negative means less amount of power requires. I hope you find it helpful.
Regards