Wow ! Sorry this problem is giving you such a rough time ! Just take it one step at a time and try not to get too dizzy in an inverted astronaut position under the dash . Never my favorite place to be but ya gotta do what ya gotta do ! Sorry if the little lady was disappointed , but we got to get the jeep running to make it up to her ! Taking voltage readings is fine , and may prove worthy if need be , i feel as long as voltage is read at all where it should be , when it should be , that is the key . Understanding that you have been working feverishly at this , I'll try to summarize .
if by jumping the two large studs on starter solenoid cranks starter , then try , with wire removed from S terminal , jumper from S terminal to battery + stud ( no jumper across two large studs )
with ignition on to see if starter cranks . Surely , engine will start as well . This will test if solenoid is working . With voltmeter connected to the wire that goes to S terminal and ground , crank ignition key to START and observe reading . A reading indicates ignition switch working .
I would imagine you have either removed or back probed all wiring to ignition by your post.
this is good too as its good to verify all circuits working to eliminate any other possible problems .
Try the tests I just recommended for simplicity , that will keep it simple so as not to drive you up a wall . You can do that with the jeep , but we need it running first . Love driving them , hate pushing them ! LOL . Admittedly , it's not typical ignition switches go on the blink , but once in a while , they burn a contact or the sliding mechanism gets sloppy and/or breaks .
Just a little testing of your patience changing them in the so convenient place their installed .
Before we send you to the parts store , we do want to be sure what is broke . I'm a perfectionist when I try to diagnose as I want to know what is wrong and why it happened . I've gone as far to remove my whole dash to find a short once . Glad I did , found three . I'm not thinking the worst for. Your CJ7 , but I'm sure you want it fixed right and fing the cause . Hope all else is good and we'll attribute this to wear and tear . Taking voltage readings would prove invaluable should diagnostic involvement get in depth. I'm thinking its a simple thing , worn solenoid or worn ignition switch . Take your time , you'll get to the root . Feel free to post anything you need.
P.S. - silly me , RE - read your post , I thought I got it right the first time , you already did verify that the wire to S terminal from ignition switch is hot in CRANK but not in RUN as it should be. Ok , we better wait for you report when you can .