I think you may have lost an inch simply do to body compression. While shooting the compound, your very low holding weight was far less than that of your traditional bow, now that you are holding a peak weight at full draw and losing the mechanical advantage of weight reduction at full draw it causes your body to compress more.
As far as your arrows flying weak, is it possible that your over spined ? I to have a NM Superior, 64" 57 @ 28 , after much experimenting I found that 50-55 spine W/ 145 grain point flew like a dream for me. No 2 set ups are the same but I thought id throw that out there.