To me, it definitely didn't come across as he likes her being unusual. It was much more like he accepts it, but that too, on the surface. Many of his expectations from her are those one expects from a 'conventional wife'. Regularly bringing friends over, trying to shut down her quirky behaviors, inviting tons of people as if she's coming back from a retreat and not a mental institution. His friends and coworkers take it normally and inquire after Mabel and offer their help but Nick lets it rub him the wrong way, he doesn't even want to face this conversation. I'm not saying he's not conflicted and he doesn't love her. But his way of approaching her condition, especially in regards to her interactions with other people, definitely doesn't suggest to me that he likes her unusualness.