Surprised you are having difficulty after seeing the video? They really do seem quite straight forward. You described yourself as being quite knowledgeable with trigger set-ups. The adjusting screws work together to achieve various low pull weights. Not just one quick adjustment here. But it will go lower than 1.5lbs.

BTW, are you familiar with target triggers in the SINGLE DIGIT oz setting? Hell, I think 1lb. is SCARY light! But 4oz?? Honestly, from my experience, using a trigger in this realm requires careful, & meticulous bolt closing. Not gonna “slam” the bolt home with authority here! I haven’t event used a trigger pull gauge in many years. I think it draws too much attention, looking for a certain number. I worry about how it feels to my index finger. Not a number on a tool.