There's something wrong there...
What draw length?
I'd expect 64# @ 28" to make 180yards
Mind it's easy to pace over a yard if you deliberately take big strides, and head wind or uphill can be a killer. I got plenty of practice pacing yardage when I used to play golf.
Arrow weight doesn't sound too bad, my 'standard' arrow is 100gn on a 5/16" shaft 28" long 3" parabolic flights.
I think a 40# should make 140 yards.
One arrow is no good, it takes a while to get your eye in for 45 degrees, so shoot 6.
Why are you using 18 strands??? Are you going to use it as a tow rope too?
10 is plenty (on a continuaous loop string I lay in an extra strand at the loop, but that's still only 6 strands at the nock!).
The other killer is holding at full draw and getting a sloppy loose. A guy at our club was trying a Hickory bow, I shot the same arrows from his bow and got 'em 20 yards further!
Del