so i have something to say about why vivenna couldn't just awaken something small, give away the rest of the breath and then take back her breath from the object she awakened. This is not a flaw in the logic of the magic system, it fits.
The reason she could not do this is because the only objects that take only one breath to awaken are Lifeless and the breath given to these dead bodies is irretrieveable. if vivenna were to attempt what u suggest and awaken some other object she would have to invest in it any number of breaths depending on the objects resemblance to a man and its relation to living material. There is no way for her to invest only one breath and still be able to retrieve it. Following your method she would have fewer breaths true, but she would still be left with more than one breath.
I suppose if she were incredibly determined, she could attempt to find an object that would take exactly one less breaths than she had to awaken and then just get rid f the object, but seeing as biochroma is fairly imprecise, this would be extremely difficult. Unless, of course, she went around creating Lifeless after Lifeless, decreasing her stores one by one until she only had one breath left. but i doubt Austre would approve of that...