Something like this is very common in novels and lyrics, and similar questions have been asked many times:
Why is 未来 read as あした?
Why are some lyrics' words written in kanji whose usual reading is not how it is sung?
Why do some kanji have furigana that are not valid readings?
Are these furigana wrong?
Reading 男 or 女 as ひと
In your case, the author want ...
As you quoted already チ is the sign of Go-on (呉音). Except 罰 is 慣用音 (which means the conventional pronunciation)
Many websites suggest チ came from Go-on while ツ came from Kan-on (漢音).
(see https://www.goodcross.com/words/19848-2019 for example)
Basically Go-on is older than Kan-on, which might explain why many numerals are Go-on.
I am not sure of what your 1)...
No, most Japanese kanji words have only one correct reading. For example, the correct reading of 電車 is always でんしゃ. Just because a character can be read in two ways does not mean a word using that character can be read in two ways. In partucular, many on-readings make sense only as part of longer compounds.
However, some kanji words do have multiple possible ...
This is くそしゃかい.
Rendaku is never applied to 社会. 社会 is a kango (Chinese-origin on-reading word), which normally resists rendaku. See: Rules or criteria for 連濁: Voiced or unvoiced syllables in compound words
Besides, the reading of this 糞 is くそ, not ふん. くそ is a derogatory word analogous to English "shit(ty)" or "crap(py)". 糞 read as ふん is ...