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.
What we have here is... failure- to communicate.