"Przyszłam" or "Przyszedłem" should be accepted
True. Added both.
Wróciłam o pracy, Is this possible?
Nope. Whether you meant "o", or "od" (which seems more probable to me), no.
I prefer 'niż zwykle' but somehow 'niż normalny' came into my head. Would this work in an everyday polish context or is it wrong? Thanks
'Niż normalnie' (adverb) is accepted here, but I definitely recommend 'niż zwykle'.
Dlaczego nie "wróciłam się"?
I think I'd only use "wróciłem się (do domu)" if I left home, suddenly remembered that I forgot something, and got back there for a moment to take that thing. That doesn't seem to work for 'coming back from work'.