The received power at RX side is given by:
Prx=Ptx+Gatx-Lctx-PL+Garx-Lctx
where:
Prx is the received power, in dBm
Ptx is the transmitted power in dBm
Gatx is the gain of the TX antenna, in dBi
Lctx is the loss of the cable from TX to antenna, in dB
PL is the pathloss, in dB
Garx is the gain of the RX antenna, in dBi
Lcrx is the loss from the antenna to the receiver, in dB
So in your case (with no cable losses) we have:
Prx = -30 + 3 - 0 - 50 + 5 - 0 = -72 dBm
Then if in that setup you reached the sensitivity when Ptx=-30 dBm, then at the input of your receiver the power was -72 dBm.
I don't understand where the -83 dBm comes from (possibly you subctract the gain of the TX antenna).