No start no crank

Try a security system reset, kind of sounds like it is knocked everything out. However, you replaced the ignition switch so it may not match with security so will need a scanner to match it up most professional models do. See link.
https://www.2carpros.com/articles/how-to-reset-a-security-system

You changed the ignition switch itself correct? Not the key cylinder? You say you can sometimes get the dash to come on but not start if you push hard on the key?

Was it a new switch or used? Are you sure you installed it with the switch in the run position?
If you jump the start relay in the power center from terminal B5 to terminal B1 does the starter turn over?
I assume you have tried moving the shifter to neutral and cleaning ALL battery connections?