Wilkinson Power Combiner Feasibility
You are confusing absolute power (dBW) with gain (dB). Your received power is +1.75 dBW. A Wilkinson has 3 dB insertion loss so your signal would drop to -1.25 dBW (1.75 dBW - 3 dB).
When using a Wilkinson as a combiner, if both your signals are coherent (same magnitude and phase) you will actually get a 3 dB boost in received power. If you're receiving two +1.75 dBW signals, you'd see +4.75 dBW at the combined output of the Wilkinson.
However, this only applies if the signals are in phase. If they are completely out of phase, they would cancel and you'd receive 0 W (-inf dBW).