You jump the large/small terminals on the starter & it will crank. You jump the starter relay large terminal to the nearby brown wire solenoid terminal (has a mini screw holding the terminal to the relay terminal) & it will crank. With the key held to start by a helper you have voltage at the yellow wire "ign" terminal at the starter relay. All correct so far? SR has been replaced so we'll assume it is good. ALL that is left is the "grn" male terminal on the SR needs to be grounded. (1) jump 12V to the yellow wire "ign" terminal to confirm it is getting enough amperage (2) ground the SR base to ground (usually its wide base/mounting bolt takes care of that but check it) & not sure a SR needs to have a good ground but we have a difficult case here so I would check it. (3) ground the male "grn" male terminal on the starter relay to nearby ground & try cranking again.