I don't think Reiichi is a bad guy after all. Kinda feel bad for him.
Reiichi isn't a bad guy, but he made a serious mistake when he tried to fix Kaoru's problems by marrying her, and it's been hurting both of them ever since.
Also, Kaoru is gay. I sense her entire bout of insecurity and now investigation into Reiichi's feelings for her is triggered by her subconscious feelings for Uta in the first place...If she didn't have a thing for Uta, she wouldn't question the marriage.
No, sorry, but very much definitely absolutely no.
I think Kaoru could plausibly find romantic feelings for Uta, once she's stepped out of her current entanglement with Reiichi, but Kaoru's infatuation with Rei isn't trivial, and even if Uta didn't exist in the story at all, Kaoru would still have to deal with the fact that Rei seems to still have feelings for Risako, was meeting her in secret while lying to Kaoru about being out of town, and she would still be dealing with the fact that he is neglectful and distant with her.
Kaoru's insecurity and investigation into Reiichi's feelings for her is triggered by the fact that there is a lot of evidence that he's cheating on her or at least lying to her. THAT is why she's questioning the marriage. Uta just gave her the emotional strength to confront him about it.