Thomas,
As I read what you wrote - it appears you have gone through a lot of tough stuff in the past few years and it has likely drained both you and your wife in many ways. Also, since she had a hysterectomy, it is possible that she is also really struggling with issues that she hasn't been able to resolve and is possibly struggling with some depression herself.

If you can go into couples therapy - that could be the best place to start. After 20 years of marriage, and acknowledging that you do still love your wife, I will suggest you not roam elsewhere without trying first to repair and improve what you already have.