Go to bowmaker.net and read the tuning information.It's good.You basically start out close,like 10-15 yds and as your flight improves,move back as far as your groups will let you.The object is to have the bare shafts impacting right with the fletched.A stiff,bare shaft will impact left of fletched(if you are a right handed shooter)and it will impact right if it is too weak.After you get it shooting good,you double check everything,shooting broadheads.You may have to fine tune a little with them.The main goal is to get practice arrows and broadheads impacting together.
Reducing shaft length will stiffen the arrow,increasing point weight will weaken it.Reducing point weight will stiffen the arrow.
It may be different for you and your setup,but when I shoot 29" 2018's out of a 50# and a 55# bow,I need 270 grs on the front end,combined point and insert weight,to get proper flight.You may need something different.It helps to have a variety of screw on points to try.I don't believe you will need any that are lighter than you have.