Checking the timing on a electronic injected engine is not what you are thinking here. Timing adjusts differently in closed loop than it does in open loop. AND the engine needs to be operating under load to be able to actually read the true timing that is being dialed in to the PCM..
If you have a scanner, it will read the amount of timing being adjusted into the system , just read the live data while driving.
Closed loop conditions are usually
At least 160 degrees engine temp
Gear selector in drive(if automatic)
Active O2 sensor
Then you can throw it into gear, stomp the gas, watch the roadspeed vereses the ignition timing and RPM on the scanner. Then you will be getting closer to what you need to know to start with
Also, if the knock sensor is hooked up and working, if it does get too much timing, the knock sensor will signal the PCM and back the timing off, roughly about 3 degrees each time it happens.Eventually it will"learn" where it needs to be.
The drive method you had for setting the timing in your first post was probably the way to go.
You can dial in more base timing, but the knock sensor should keep the advance curve from going to an excess , which could cause engine damage.
Fact is stranger than Fiction