There is no real "sweet spot"
There is too much mythology on this issue.
The torque specs are there for a reason... but people pay way too much attention to them.
A minimum torque is given to allow the barrel nut to be at the necessary torque to general not back off.
Then - you simply tughten the barrel nut until the next gas tube hole can be aligned. Sometimes this is 31#. Sometimes, if the nut is just barely past one gas tube alignment, and has a long way to get to the next one... it takes a TON of torque to get there.
I have seen barrels that loosended off in the field. I did two installs on AR pistols a while back - and both shot loose (aluminum barrel nuts)
I have seen a 20" rifle shoot loose, which results in the barrel nut just rocking against the gas tube (no big deal) and the barrel is now allowed to rotate in the upper receiver slightly, allowing for a tiny amount of windage change (not good)
Neither affect reliability.... but the torque values are there for a reason.
That being said, I never use a torque wrench. I snug them up good, three times, then tighten to the next gas tune alignment position. It doesnt hurt to use the torque wrench, if you have trouble "feeling" 30lbs. My elbow "clicks" at 30# now.
(and I ignore the 80# max stuff) You tighten to the next gas tube. If that goes over 80#, so be it.)