RE: Who makes a 2-3 degree offset fletching jig??
Until you decide what accessories and setups you want, and stick with something for awhile. I would not blame the bow for speed variances.
It is not unusual for a bow to flip-flop a few fps now and then. String creep, heat, cold, humidity, dry, damp, wind, etc., will affect speed. I would not be concerned about 3 fps.