Whatever the rifle is telling you is what matters. Regardless of what the manuals claim.

I've worked up a few loads in the same rifle with 87gr vmax and never reached pressure signs all the way up to 3,250 fps.

Keep that load around 3,200 fps max and you'll be safe.

A good gunsmith should be able to re-throat the barrel with a throater for very little money. You can purchase a throater for around $125 form PTG and re-throat it yourself. No need for a lathe either.

I gain about 50 fps when slightly going into the rifling (but not jamming). Once the projectile gets jammed into the rifling (as in the bullet is stuck and can't extract a live round) the pressure goes up drastically.