Why my touchpad is so sensitive?

I have Toshiba TECRA R840. The touchpad is working fine, but it is too sensitive. For example, when I was typing, my hand did not touch the touchpad, but the cursor is moving and clicking. It's like you can move the cursor with your finger 3cm away from the touchpad.

I cannot turn it off too through the keyboard.

In the end, I teardown the laptop and plug out the touchpad cable. However, I still want to fix it or perhaps only change the touchpad (but, it's hard to find it). can someone help me?