I'm just going to ignore all of the red flags from your posts and get straight to it... this person does not belong working on your vehicle.
"It shot out really well." - not what I want to hear when I ask about fuel pressure.... I'm expecting a measurement in PSI or kpa not inches through the air.
"that's in the steering column... I know it's not that" - outstanding, he can locate your ignition switch.... however, it could EASILY be that.... when they fail you'll get all sorts of interesting symptoms. It's also fairly inexpensive and pretty easy to replace.
"he also checked wiring" - wonderful... but, of the literally hundreds to thousand plus wires in the vehicle, which ones did he check? There are no less than NINE grounds under the hood alone. If he's not experienced in working on these trucks, he has no business touching the wiring...
These vehicles are complex, advanced pieces of automotive engineering. It's many systems are integrated and interrelated and the failure of one can rapidly and very negatively affect other systems.
We need more info to help you. Please describe, in detail, what happens when you attempt to start your vehicle, as in "fuel pump comes on, starter turns engine over but engine doesn't fire". or "turn key and nothing happens".
We literally have some of the most experienced trailblazer owners in the world on this site and we are all willing to help.