I don't know if this will help you, but I'm in the UK and have some understanding of the NHS.
I went through a really, really stressful situation about 9 months ago (my partner left me with a newborn baby to move in with another woman) and it nearly killed me.
However, when it happened, I visited my GP, I was referred to a crisis mental health team. They visited everyday at first, then rang everyday to talk and check I was okay. They were amazing.
Would something like that help your wife?
Have you spoken to your GP about how you feel?
How old are your children - are they at home all day with her?
Have you thought about contacting Alanon to help you?
xx