This is somewhat OT, and I am not as eloquent as you both are, so I'll just say this:
I will agree with you that Clark should have shared the secret before asking her to marry him, but even then (emphasis mine) he wasn't completely, absolutely sure she loved him as much as he loved her.
Lois had just risked her own life to save Clark's parents. I'd take issue with his claiming that he still wasn't sure about how deep her love was for him, as
Clark and not Superman, at that point. (I am obviously not a fan of the "I needed to know you'd marry me for me" explanation.
)
