"don't blame yourself for letting her do those things?"
IMO he has no control over her, he only has control over himself. If he stayed and aided and abetted then he's enabling her to be the mess she is. His relationship is based on codependency which is a form of addiction in itself.
I stand by my opinion that this man needs therapy as much as she does and if they ever stop "waiting" to get therapy,* her councellor will want to see him and likely the children as well, just as much as he/she will want to see his wife.
This kind of dysfunction rubs off on everyone within the family.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion