I'm not sure what an NGX wall console is, but if you have one, then yes, the device you linked to connects to the wall console and the I/O Linc NO and Com terminals.
The log is a good resource, but you don't need to drop everything. Just make note of the time and search the log for what occurred at or around the noted time when you are able.
If you set the ramp rate to 9 min, then the actual ramp rate is 0.1 sec. That's because the maximum ramp rate for Insteon devices is 8 min, not 9. The 9 min ramp rate is included because the very earliest Insteon dimmers did have that ability.
Yes, X10 devices can be a problem. Each HA device absorbs some of the signal, that includes both Insteon and X10, each absorbing both signals. But, Insteon power line devices repeat the signal, X10 modules do not.
If Control 'manual controller' is switched On
and Control 'manual controller' is not switched off
Then disable schedule program
Else enable schedule program
The statement in blue causes the Else statement to execute when the device is manually switched off.
You are correct. The on-level is the level of the load, not the button. For any on-level the button is illuminated, but for Off the button should be unlit.
Create a scene that contains only the Off button. Write a program to turn off the button
If Status 'FanLinc Motor' is switched Off Then Set Scene 'Fan Off Button' Off Else - No Actions - (To add one, press 'Action')
It's as you surmised, the number of fans is inconsequential, just as the number of bulbs in a fixture/chandelier. It's the total load that matters. Also be aware that starting a motor draws more current than running one. An overrating factor of 1.5-2X is usually appropriate.
Anytime an Insteon device controls or responds to one or more other Insteon devices a scene is appropriate and preferred. If a condition is involved, then a program is required. Programs can control scenes as well as individual devices.