When referring to tweaking the resistor values to lower the bias are we referring to R7 and R10 resistors? If yes would replacing them with variable resistors make the job easier?

Yes.
Vbias1 is about 0.667V and Vbias2 is about 0.57V in the simulation.

on the transmitting end R3 is 1k but on the receiving end R1 is 2k, except for that they seem the same circuits, why is there this difference? Is it because of R6?

Yes.
It's because U3 has a gain of two to compensate for the 0.5 attenuation from the 75 ohm impedance matching resistors, and U1 has a gain of 1.

is R9 mounted on the transmiting circuit or receiving circuit?

The receiving end.
R6 is at the transmitting end.

 

Thank you for the awesome clarification, I will start gathering the parts so I can begin building, I will update this thread after I build it to show the results
Thank you again for your teachings and effort to help