with your 2nd upper degree, it's definitely civil service > big4.

idk how long u will take to earn 5k/mth in big4, but i can tell u that 5k/mth in CS is very possible n achievable within 5 years.

staying past 7pm is literally unheard of in CS. why slog so much in the big4? especially if u do not know if u will resign during the peak period of working until 2-3am daily?

even if u can tahan working until 2-3am daily, u might not be promoted in big4. but i can certainly tell u that u WILL be promoted in the CS with your 2nd upper from local reputable uni (eg NTU).