The very same dock where Clark had been discovered half-frozen and without any memories.
Now that she knows this detail she can move forward with other details. She knows that Clark was never directly exposed to kryptonite by Luthor.
Lex hadn’t exposed Clark to Kryptonite when he had him kidnapped, she had.
Not really, it was totally an accident.
Lois pushed away this guilt, because it was irrational and conditional.
I am glad she accepts that.
If Clark hadn’t happened to swim up to the same dock where she had disposed of Lex’s hideous gift…
Or if he hadn't been so curious about the shining, glowing thing in the water.
If only she had seen that Superman and Clark were the same man, or that Lex was an unreasonably jealous megalomaniac…
Well, at least she realized these things before doing anything truly stupid, like getting engaged to Luthor.
Lois sighed. No point dwelling on the should’ves and would’ves. There wasn’t a way for her to change to past, so she needed to focus on the facts.
I think you want to say "change the past".
Were they rubies, glass, or did Kryptonite come in other colors?

the third answer is right. Now all she needs to do is learn the effects of Red-K on Clark.
Had Lex really expected her to wear it, or just kept it in her apartment in a jewelry box?
Probably the former if he wanted it to be a way to kill Superman.
Did Lex know how much contact she actually had with Superman on a daily basis,
Fortunantly no.
or how close they had become?
Well, he thinks he knows this, and if he is wrong it is only because he thinks they are closer than they really are.
FACT: Lex, the Voyeur, had bugged her apartment at some point during the previous summer.]
Although even this is more a consequence of what he knew than the other way around.