I also love this book and find the theoretical link interesting, but I consider that there is a mistake in the presented syllogism.
First, you say, based on micro theory, that utilities cannot be measured nor compared. OK, grant it.
Then you say that, since the pill has “chemical effects in the organism that can be measured”, now the utilities could be compared. Ok, no.
What I think you are referring to is to the effect on dopamine or oxytocin, right? This is what could be measured thanks to the pill.
But, these neurotransmitters can be measured even though the pill is not taken… So the pill will not make utility levels comparable; neurotransmitters can be measured without it.
Now, it could be thought that since the pill can manipulate these variables the level of happiness could be equalized. This is also a misconception of neuroendocrinology: we both could have the same levels of oxytocin and be unequally happy.
DFARHUD, MALMIR and KHANAHMADI (2014) argue that: “Then, the articles divided into five sub-groups (genetic, brain and neurotransmitters, endocrinology and hormones, physical health, morphology and physical attractiveness). […] Results of studies on genetic factors indicated an average effectiveness of genetic about 35 -50 percent on happiness. […] Neuroscience studies showed that some part of brain (e.g. amygdala, hipocamp and limbic system) and neurotransmitters (e.g. dopamine, serotonin, norepinefrine and endorphin) play a role in the control of happiness. […] Physical health and typology also concluded in most related studies to have a significant role in happiness.”
Hence, the pill would just address one variable of all the others which affect happiness.
To conclude, yes: the pill would make everyone happy and perhaps surpass a threshold in which a fictitious socialism is implemented. Nevertheless, it would still be impossible to measure and compare the happiness levels objectively.