Perfect calibration is not needed for lawn equipment. the key is Consistency. As long as All head or sump Bolts are Torqued to the Same Value, a couple of inch-pounds off won't hurt.
Low Click...Bad Battery. I don't care how new it is. Lately even new batteries have not been dependable. I'm blaming the EPA. Get a trickle charger and charge them at least a couple of times a year.