The change in POI was due to flexing (bending) a very light weight barrel by pulling on it externally.
As far as rate of twist, in my opinion, you have a good one for most uses.
1/9" twist: will stabilize bullets ranging in weight from 40 grains to 75 grains. And yes, it is actually the LENGTH of a bullet, and not the weight- but heavier bullets are usually longer, so it works out.
For hunting, would find the heaviest bullet your rifle shoots well, zero with that bullet, and don't look back.