There is a bell curve for your optimum spine and there is a bell curve for your particular bow and arrow combination when it comes to speed.
For a 45# and whitetails a 450-500 grain arrow is a good combination. 10-11 gpp gives you good trajectory and good penetration.
Depending on where you hunt, I would refrain from using 2 blade broadheads without bleeders.
It is great if you killed the deer, but it stinks if you can't find it due to a lack of bloodtrail.
In thick cover, a Wensel Woodsman or a 2 blade broadhead with bleeder blades is very much recommended. This is especially true with heart shots during the fall (I had two of these with zero blood to trail due to shooting only 2 blades at this time). Never had zero blood trail with Wensels Woodsmen or with the bleeder blades.