I'm so sorry that your boss isn't supportive of this. Too bad there isn't a legal option for that.
I pumped for months while my daughter was in the NICU and I never got much from pumping, even with a hospital grade pump. Babies are always better at getting milk. I still can't get more than an ounce or two when I pump, but Willa is gaining weight steadily, so I know I'm producing what she needs. I fretted that Ada wasn't getting enough and supplemented her (also so that I could pump for her sister in the NICU), but I think having the pump really effected my confidence.
I got more out of one boob usually, but it was never the same one. I don't know about the supply, but at work, have you consider hand expressing in the wash room on the breaks you are allowed to have? You could also get a converter for your car and pump while driving