Poor Clark. First he loses his wife (literally), then his mother-in-law accuses him of being guilty of the crime, before dying of over-drinking. Then after her funeral his sister-in-law makes moves on him. Lois really hasn't been gone that long. What? A few months perhaps. It seems a bit early for Lucy to give up on her sister. It doesn't show much sisterly concern for her sister. It does show, unlike her mother, that she doesn't believe that Clark was involved. If Lois had died instead of just gone missing, would Lucy have made her move so soon? I doubt it.
I'm surprised that Clark still saw Lucy after that first uncomfortable situation. He had every right to break off the relationship, then and there, because she was being inappropriate. I'm surprised he didn't push her off him and onto the floor. I found that whole scene disturbing and uncomfortable; I can imagine how Clark felt. He told her "no" and she kept trying to make moves on him, even for years later. That shows a blatant disregard for his feelings and for Lois.
Lucy should consider herself lucky that he foisted her off on Jimmy. I'm not so sure Jimmy was just as lucky though.
I'm not surprised that Clark didn't move on. Unlike everyone else, Clark knows about time-travel, and his prime suspect is a time-traveler. If he ever considered moving on and started dating, or became intimate again with another woman, I could see Tempus choosing THAT moment to bring Lois back to show her how unfaithful Clark had been. He keeps hearing her heartbeat. He keeps sensing her and sensing some kind of anomaly in his bathroom, which could indicate Tempus.
I wouldn't be surprised if others didn't suggest that Clark 'move on', but Lucy's actions seemed to speak the loudest to him.
We knew it was going to happen. Poor Perry, never recovering the loss of Lois.
I've seen this in life. Everyone worried about the husband and his aliments, and then the wife ends up going first. Martha's stress for caring both for Jonathan and Clark finally took its toll.
At least, he still had Jimmy around; although, if Jimmy became involved or married to Lucy, I could see Clark distancing himself from them due to her years of inappropriate actions. I think that would be difficult for Clark to either forgive or forget.
I could see the stress in Clark's personal life leaking over to his Superman persona, giving him a more intense and serious demeanor. I wouldn't be surprised to see him channeling his anger and frustration through Superman and keeping his grief for his Clark persona.