Going back to your original post I would try to solve this problem first, although it's possible there may be multiple issues.
You have TIP start so the key sends a signal to the ECM, and then the ECM is what sends the signal to the starter. The switch on opposite side of the column is a known culprit. Check that and then proceed to the next step in the signal chain. Here is a good example of this situation:
If that doesn't solve the issue you can check the IOD fuse for the wireless control module (WCM). There is a TSB for this issue - Technical Service Bulletin 08-007-08. Essentially you just pull the fuse for 30sec to reset and then try starting again.
Next I would measure the voltage at the starter relay. You need primary voltage present for the starter and for the signal. You can jump the relay and see if the starter engages. If so, the downstream wiring or solenoid are not the issue. If you're not getting a signal to close the relay then the issue is somewhere between the relay and the ECM, or the ECM itself, assuming all the other checks I listed above were ok.
Note: Since you said you tried starting in 4low that rules out the clutch interlock switch.
