Okay so, I made progress on the frequency brown townysis by trying to swap out the 3 most frequent letters in the cipher text (AIT) for the most frequent letters in english (ETA) in order.
By swapping A for E, I for T, and T for A, we get:
YIWATPMPITTBIFIIAAAIWTKHTPAWV IRLAFOTAVAATHDISAIATS
into
YTWEAPMPEAABEFTTEEETWAKHAPEWVTRLEFOAEVEEAHDTSETEAS
I can already recognize some English letters and terms, like
YT WE APM PEA ABE FT TEEET WAKH APE WVTRLEFOAEVEEAHDT SET EAS
Soon, with more effort, we'll be able to know what OP, Pea Abe, are going to set, and whose teeets they are mentioning.