Definitely agree with the idea that they need to make Nishikata act like an actual married adult, rather than like he's still in school.
Him still competing with her is one thing, him having trouble holding her hands is another.
Though I think that 47 was actually rather good about that, since it's less embarrassment over the idea of KISSING YOUR WIFE, and more embarrassment over the times she pulled stuff like that on you when you were younger.
I think the best way to think about it is that the times we see Nishikata act like that are the exceptions, and not necessarily how he always acts.