I bought some Duke #4 traps, and I can’t get anything past 2 lbs. I’ve even broke one brass screw trying. Tried another trap, 2 lbs. what am I not doing correct??

Try adding a washer between the pan and pan post when you tighten it. And use a little heat to melt the wax out of that area if you have waxed them, even roughen the surfaces with sand paper.

… may need to squeeze the pan post closer together with a pair of vice grip pliers

make sure the pan notch and dog end are square.

Don't worry about it they will work just fine the way they are.......jk

^^^^
Yes, with prices of skunks and maybe fox being worth more than coyotes 2 lbs is plenty. Some fox trappers would say its too high.

You’re way over thinking it. 2# is more than you need. Set heavy and don’t worry about it…let the sets work for you and let God sort them out.