The bridge arrangement appears to be consistent with this:
from The Wheatstone Bridge Circuit Explained
That's not a strain. Strain does not have units of length. Strain is elongation divided by length, so it is, nominally, unit-less. Since it is often such a small number when expressed as meters per meter, it is often referred to in terms of um / m, or microns per meter, or micro-strain.
One way to test whether your bridge is working is remove everything from it, apply some voltage to E+ and E-, and use your DMM to measure the resulting voltage across A+ and A-, for no load and full load. Compare the measured voltage to the voltage calculated using the properties of the strain gauges, configuration, and applied voltage.
One way to test your HX711 is to ditch the calibration part, output raw readings for no load and full load, and see if those match the expected output (obtained by calculation).