I suppose I can understand it to a degree, but for an acclaimed investigative reporter, it doesn't reflect well on Lois that she can't figure out Clark Kent and Superman are the same two people. Even with glasses.
As for eating and sleeping (not sure if that's a real question), I don't see why not. Anything could be explored/addressed and I certainly wouldn't mind. Wouldn't surprise me if both are different from humans.
You should read some of the other posts on this thread, they go into detail on how his secret is kept from Lois, and how this coudl be translated to a movie.
The reason does not need to be perfect, but just direct the audience away from it.
Easiest reason is how people build up their heros with mental exaggeration.
The other issue is that identity is much less about specific facial features, and more body language, speech patern, voice etc... Non-Verbal is for example about 90% of human communication.
Other issues are a seeming 3-4" height difference with Clark and Superman.
As Clark, he would slouch -2 or -3 inches, and wear flat sole shoes -1 inch compared to normal footwear every one else has on.
As Superman he would stand with good posture, and wear boots with a normal 1.5 inch heel, and 0.5 inch padding on the inside of the boot. The result is him seeming 4"-5" taller than Clark. That is a big contrast.
Add that to voice and body language and it should be convincing enough.
The last thing to add to it, is that because Superman does not wear a mask, no body looks for his secret. By not wearing a mask he gives the impression he is superman fulltime.
That way, as Clark, he could wav it in their face, and claim to be Superman, and people would think he is joking. Humans refuse to see what they are not looking for.

t: