Actually I think the SSM part of it is the only part you are close to - 12_51 and his wife had a fairly good relationship with him being supportive and kind to her. That's why it was so easy for him (No excuse but it is the reason) to let the sex issue slide. He thought the rest of their relationship was fairly stable and just did not give sex the priority it deserved.
"What does you wife think was the 'reason' for your LD?".
He was tested at the very low end of testosterone and is on a prescription. So there was a medical reason he is addressing and the other mental reason he needs to address for the future is the fact that he took his wife for granted which is why he did not actively pursue the reason for his LDness sooner.
Mojo, I understand that your marriage had plenty of other issues so it may be hard to explain how good marriages end up in trouble. In good marriages couples can feel so sure of themselves that when something goes off-track (sex, time together, regular talks, etc.), you do not immediately react because you are "confident" in the goodness and security of your great marriage. That is also why I think his apologies to his wife need to be in the tone of "sorry it took a ton of bricks on my head to figure this was a real problem." Right there he owns up to his mistak and explains that her leaving IS what got his attention to take care of his LD issue without getting off-track.
From what I have read, overall, 12_51 is on the right track. He is not becoming someone new; he is getting back to the man that his wife fell in love with in the first place so she will recognize him.
At least that is how I have read his situation so far.
But what is happiness except the simple harmony between a man and the life he leads? ~Albert Camus