How about option 3.
Father leaves but does not blow things up (da or df), and speaks freely with their child down the road when the child becaomes able to understand more. he will need to be honest with his wife, and slowly work on her. He may even have to insist on taking the child to other places other than meeting, which of course will cause strife.
The child is one. There is no reason to think about explaining doctrine. At the most, several years from now they may want someone to study with him, and that is as much the dads call as the mothers. They cannot force the child to study as long as the "unbelieving mate" has decided that is not ok. Focus on the kid.
No need to get disfellowshipped. No need to DA. Just leave. As long as you don't try to convince others, your conversations with your family cannot be legislated. Don't underestimate the power a year of fading gives you. The congregation is a bubble. one year out, and they forget about you anyways because they are "busy with the work".
Just my two cents of course. Kind of my similar situation, and that is how I am handing it. My wife if now waking up and we will all be together. My small child doesn't know the difference.