First of all, there are numerous ways to express "even" in Japanese, so see the link at the bottom titled「ですら・でも…」if you would like to see an excellent explanation of those.
Second, to your example specifically, I think you are possibly confusing （にとって）+ the particle も; and the particle に+（とっても）.
The X+にとって construction means "to/for X" (e.g. 私にとって to/for ...
This 足生やした not an idiomatic expression, but simply "(which) has grown legs" or "(which) has legs". 足 is "foot" or "leg", and 生やす is "to grow" or "to wear (a beard, etc)". He said the crowd of soldiers is almost like a walking country. This is a rather unique metaphor.
I have not read the story, but apparently the character pictures emotions as squares, triangles and circles. I got that from a comment found here, which says
So as long as the person who wrote ...
I think it is referring to the practice of expressing unintelligible speech in novels or manga with a sequence of random-looking characters like
△◇ ★彡◼️◇ ¤♡☆_♫ etc.
So, basically, something which cannot be expressed by words but possibly by some symbols/images.
I have not heard of other meanings, but as symbols like triangle are sometimes used to refer to e.g. words / parts of a sentence when eg explaining grammar, maybe the sentence was taken out from such a contect, and it was preceeded by the actual sentence?
This 姿勢 (literally "stance") refers to a "way" of doing something, and 自分の生きている姿勢 is roughly the same as 自分の生き方 or "my way of living".
(living a life embracing the sense of guilt) may have been one of the (possible) ways of my life, and ...