You are overthinking it, it's just a misspelling of "FUCK." As spelling FUCM (with the intention of spelling FUCK) in all caps results in Apple's autocorrect to not fix it because its a curse word and because it is in all caps.

A euphemism for “kill me” now that composting oneself after one’s death has become popular.

Stands for "First United Church of Michelle"

Michelle Phelps is also a very religious women and has her own church. If you believe in her and worship her and try hard in everything you do She WILL bless you.