Steel, Actually you both are ripe candidates for a midlife crisis/transition. Go back and take a good look at the timelines and the triggers. You were strong enough to recognize that something was off for you and sought medical assistance. I commend you for that.
Your wife, on the other hand, has a physician that is being cautious and yet maybe she hasn't told him the full extent of her symptoms. The lack of sleep is one of those symptoms and and it's true that in some cases lack of sleep will make you feel worse, but if it's been an ongoing problem, then someone needs to dig a bit deeper into the situation and the symptoms. Has she given any indication as to why she can't sleep? Worry, anxiety, too much caffine? Has this been an ongoing problem for her or just fairly recent?
I hope and pray that your wife will opt to seek medical assistance elsewhere and get something prescribed for her "mild" case of depression. Unfortunately, she has to be the one to make the decision to seek further assistance. It's hard trying to help them when a medical professional has stated it's a "mild" case.
Please continue to take your meds and I hope that you both are feeling better soon and can get back on track w/your marriage. It's very difficult when you both have had the timelines and triggers that you have had.
Hang in there. Things have to start looking up for the both of you very soon.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.