I have to agree with the later recommendations of NOT getting a 500 spine. Good golly. These would be so underspined as to be rediculous. At 29" they're more suited for about 50#. You're probably closer to using a 300 spine than you think.
I shoot a lot of 500 spined arrows and at 27# (arrow length and draw length) about the highest they tune well is 63#. It can vary with the aggressiveness of the cams, but at your specs they are way off the chart.
Of course there is a way to easily find out without spending any money. That is to just turn the bow down to about 65# and see if things get better.
I also agree that you might be having a contact issue. Underspined arrows usually won't group with broadheads. They'll fly erratically and scatter all over the place. Of course, the same can be said if your fletching is whacking the rest.