He stopped by a grocery store and picked up a few essentials before returning to the Lois’s apartment door around eight.
As much of Lois is her own unique person, I think that should thus be "to Lois's apartment", no the.
Oh,” he said modestly, knowing full well that was her way of saying ‘thank you’. After last night’s thank-you-for-not-sleeping-with-me goodnight kiss, he decided he would do anything and everything possible to earn her gratitude, include make her a healthy breakfast. He moved into her kitchen.
I think that should be "including making her".
“Do I remind you of your romantic hero?” Clark asked, not only because he was perfectly fine with her thinking of him as her idealized romantic hero, and because he was a glutton for punishment. He turned and started them up the stairs to his apartment, his hand resting on the base of her back for a moment.
I think with the "not only" set up, "but" would work better before "because" than and.
