Emotions are at least in large part determined by biological factors, though.
Absolutely agree.
In that sense they are considerably more measurable and objective than "God".
Yet, they're not. You can measure the biological and physical things, but you can't find the emotion in the chemical formula. It's an emergent property of the reactions and the processes as such, which means that these things aren't just what they seem to be on the surface. You can't for instance deduce how it is to move your mouse around on the screen and click on a window just by looking at the binary code for Windows. There's more to things than just the numbers and quantities measured.
Just for fun, can you give a number of measurement of joy? What units would you use?
Not that it is all that difficult to get at least a sense of what is meant by "God", either. There is a cluster of most frequent meanings.that, while probably not all-encompassing, is at the very least quite useful to keep in mind. There can be little doubt at this point in history that for many people "God" is a personification of a mystery of the creation of existence and/or a mystical source of virtue itself, for instance. In other circunstances it can be a crutch of sorts, an attempt at earning debate privileges, etc.
Also, take into account that the word itself, "God", hasn't been around for more than some few hundred years (old English), and it has changed definition and meaning from its roots in Latin (numen), and to add to that, there's been several philosophers and theologians disagreeing with the anthropomorphized version of God and suggesting more pantheistic and naturalistic views of the word hundreds of years ago, so this who personified God is just one version that has been contested for quite some time.
It is of course conceivable that there are outlier cases which are not all that well understood or described by those typical situations, but I don't think that is particularly noteworthy. Knowledge and understanding can and will have boundaries without that truly implying transcendence.
Not sure what you meant to say there. It's most likely me not having my full capacity of my chemical reactions in the brain at the moment after all those great Christmas beers I just imbibed.