Since snails go really slowly, and it says "SLOWING my thoughts...", we can interpret that he/she isn't thinking of things very fast. Our brains can think things so fast, normally we don't even have to think about it. (Wow, how many times can I say 'think' in one sentence?) But he/she is having that process slowed, probably because he/she can only focus on how cold he/she is.
C. The idea behind "fixed form" poetry is to make it look like a picture when you're done with it, and it's hella hard to do that and rhyme at the same time