If you've never tried the screw and washer trick....try it. It can chew up a target that has a lot of miles on it.....but it let's you stack weight until you get tuned. Once the arrow flies true, pull the whole stack and screw and weigh it. If you can get within 20grs you'll probably be golden.
Once that's done, grab a fletched arrow and a broadhead and let them fly along with your fletched arrow and a bare. If you are correct, they should all shoot to the same point of impact at 30yds. Don't be alarmed if your bare is not parallel to the others....just where it impacts. If it hits sideways, you obviously have issues, but 15* out is typical.