The trigger pull and the safety adjustment are independent. When your trigger is set light the trigger does not completely engage the sear making the rear of the trigger impede the safety movement. If you push the trigger forward in its current light setting you will more than likely be able to operate your safety.
Adjust the spring till you get full engagement(as you close the bolt the sear is making contact with the screw). Then adjust your safety.
FWIW, stop trying to get a target trigger out of something that was designed to be set at a minimum of 3.5 lbs or more.
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