Yeah, it was likely a couple of weeks because Perry (and this was a major point of dispute when the movie came out) specifically said that Lois was being put on two weeks' leave. In that time, her silence and willingness to protect Clark and the secret allows him to trust her and things develop from there.
So Donner ripped off Thomas Carr and Richard Fielding/Robert Maxwell (the director and writer of the first episode of
Adventures)?
Formula and homages.
For example: the sequence (in
MoS) where the Jor-conscience tells Kal about the escape from Krypton, the rocket looks like the one from
STM is a homage not a rip-off.
Clark asking why he's so different is part of the formula, and was used in episode 1 of
Adventures (where he's 12),
STM where he's pushing 18, and, again, when he's around 12 in
MoS (although it can be argued it was used again in the pre-tornado scene). Formula, not rip-off.