Proportional

[Brownlie]

I couldn't tell you much on the convention of gimmicks.  I suppose you could be more direct here, but that would alter the tone (to me at least). There are a lot of feminine endings, did you intend this?

too much of a gimmick?  

Like a guttural street mongrel, -- This seems to indicate muts, and possibly doggerel if you mean to be flippant. I suppose it's good that you begin the list with the Irish bit then.
I am half Irish, one quarter German,
one quarter Swedish, a frac/
tion may be Luxembourg; mother -- The semi colons make it somewhat choppy, but it is not incoherent (plus I hardly use them so that may be why it's choppy).
told me Granny visited there once
before the turn of her century- before her 100th year?

In the primary grades we are taught frac/ -- Is primary grade still used as a term? Maybe include that you are also taught nursery phrases with your fractions. It may make it read more smoothly, or it may not.
tions: step on a crack, break my mother's back
her two halves like two kinds of luck;
we always walked on dark streets
just in case -- This is quite fascinating because the cracks seem like cultural borders. Oh and period here?

There are seconds, minutes, hours, -- Very beaty break after this line.
even years; all these small moments
drop by drop, are filled with frac/ -- Drop by drop? Are you referring to an hour glass? This quantifies time (to go to that level of analysis). Do you need drop by drop for your meaning?
tions; how we spend them is the hum
of secrets never shared -- Period, what is this hum of secrets?


The fragments of poems: words,
lines, images, the murder of crows
when they lift to ease into other trees -- Into other may be spondaic hiccup (I think that's how you use spondaic).
to break the hoary silence of winter,
branches black thick on white, frac/ -- I think it may be good to describe the crows on the snow covered trees more clearly and with exact imagery and the like.
tions of life; it takes all the time left
in the world just to catch our breath -- Period or other punctuation. This sounds good and it may mean something or suggest something very cool. I'm not sure here.

There's some cool stuff here, and I left some comments.