RE: field point vs. broadhead impact point
Just what is your bow tuned for? Paper tuned? That isn't tuning. That's just seeing that the arrow leaves the bow cleanly. It's rough tuning. It doesn't show you what the arrow is doing down range, and that's where it counts.
As mentioned, Easton's tuning guide will help you get things straight. When your bow is tuned properly both field points and broadheads will hit the same place and fly well getting there. This assumes that your arrows are spined correctly and you have helical or at least offset fletching to control the arrows.
You have in the past assumed your bow was tuned, but then you shot braodheads and were hitting a little high. Well, those blades up front were just showing that your bow was not tuned to the nth degree, but close. 1/32" in nock point adjustment would have probably made both points hit the same place, and you'd have never see the difference in flight or paper shots with field points. Broadheads emphasize those little imperfections.