i can't recommend enough for everyone to learn more about chaos and randomness (hope i'm not repeating myself too much here) without trying to put order into it.
it should be taught from basic school alongside math and history until doctoral alongside philosophy 404 and programming logic.
that is, supposing school should even be so scholar like that...
now...
you really need to get out of google to test issues with google even if not for anything else, because it's easily possible to do so (unlike testing for other forms of life such as the carbon based ones we know, for instance).
your tests there seem to average out at around 85mb/s which is a rather high speed and looks stable enough to me. even the bumpiness is expected under any normal circumstance. no idea what other meaning to extract from them. but they say nothing about copy vs sync.
sorry, but i won't bother with my google api and hopefully i won't need to bother with testing as well. just let it go, i don't need help there. 
(i do need help on my other topic, though. have you seen it?)
on another note: more than testing outside google, i used google for about 20 years and i had been on gmail before since the beta. i also can't stress enough on how blind and stupid i was to trust google with organising my data. i'm talking about the very core thing that google have always promised: offering a good way to organise the world data. they're actually terrible at it. despite some good deeds now and then. just terrible and way more biased than almost everyone would like to believe. please, do yourself a favour and give an honest try outside their system.