It sounds like you have a voltage drop at the ignition switch.Do you have a volt meter or a 12 volt test lamp to perform some checks?
Do you have a scan tool or code reader?
Have to tried to swap the starter relay? Do you have a code reader
If there is power at all times on one cavity and power on the 2nd cavity during cranking you either have a bad relay,ground (G106) .Monitor circuit 3 the purple wire at the starter motor solenoid if you have voltage there your starter motor is bad.If you jump the starter motor solenoid circuit at the relay it should crank and start.if it starts remove the jumper.
Check for voltage at the starter motor purple wire. if you have voltage during cranking and to engine won't turn over the starter motor is bad.
Click accept if you are satisfied with my help.