It's pretty common to leave in Japanese honorifics and Korean "oppa", "ahjussi", etc. It reads fine to anyone, as long as you leave a footnote. That said, do what you think sounds best.
Hmm I'll think about it. Same goes for "nuna" too i guess, which uses haneul all the time. However iirc there wont come many backflashes about mr. Scientist's wife
thank you so much for this translation! i'm also wondering whether the other characters from seasons 1-3 will come back or is the story right now a flashback & will there ever be a english translation for season 5? just asking :)
S4 got 25 chapters.
Since haneul and heyool appeared in the prolog and got some cameos up until now it's safe to assume they'll come into spotlight soon, i think. Also nara already appeared actively a few times! But see for yourself and keep reading
If you mean official ts from webtoons... idk. If you are impatient af i actually already translated s5 but it was my very first scanlation project so its quality isnt consistently good~ you can find it on some other page if you put some effort into searching i might redo it after S4