It sounds like you may have a lot of issues going on here. First of all, where did you buy the bow from? You should have your draw length checked and adjusted correctly before you start changing or buying anything. If you bought it from a dealer, they should adjust it for free. If you bought it somewhere else, you may have to buy a new cam. After that, take your Carbon Express arrows and cut them to the correct length. Once that is done, you should check for fletching clearance. The Bowtechs shoot so fast that a lot of rests do not get out of the way fast enough and sometimes your fletching will hit them. What rest are you using? After you have eliminated any clearance problems, then I would paper tune. Adjust the rest and/or nock to get that correct and then start shooting at your target. Switch between field tips and broadheads to see where they impact and adjust your rest again if needed to have them hit the same spot. After that, you should be shooting well with those arrows which I would call "heavy." They weigh 12 grains/inch. I wouldn't mess with a light arrow this year as you would have to re-adjust your bow. Next year, you can start messing around with some lighter arrows to see which you prefer.

Another tip would be to read everything you can about archery and bowhunting. There is a lot of great info on this site about equipment, bowtuning and form. I've been shooting for 20 years and have learned a lot from this site in the past year.