We can go around in circles over the big question as to whether or not Lois knew.
My position is that Lois always knew. From day one Lois knew, there was never a day
where Clark fooled her. There were times when she couldn't prove it, but she still
figured Clark was Superman. Don't even try the glasses were hypnotic bit. But as
their relationship went on, with Clark not proposing for years, she figured he would
propose eventually or else she gave up on that happening. When Clark finally did
propose, telling her everything, she feigned surprise. Women sometimes feel the need
to cater to the male ego.