In this particular need I understood that standard editor was not the right tool.
Well of course not, because you want information from Live to control the LEDs. That doesn't mean you can't configure the SS in the Editor though. Just because you need to go outside of the Editor the the external LED stuff, does not mean that you need to completely abandon using the Editor. For your particular use case all you need is one M4L device. You don't need to do everything from within Max.
Why do you need to send messages via network to a max patch? Do all that stuff within the M4L path. It seems you are overcomplicating things a bit.
You can't set the sensitivity directly from max. Sensitivity is basically as scaling factor. If you want the keys to trigger more easily lower the on thresholds in the Editor
Not sure why you would need to adjust the sensitivity from max anyway - why not just use the Editor to dial in your settings? Do you need to adjust sensitivity in real time?