I know you avoided sharing details, however, some might help, just to get a better picture of who you are, and what went down, prior to all this. Did you have one or more affairs? Were they long term? How long were they going on for prior to D-Day? Are there any special circumstances, such as dating a family member or best friend, etc?
There is a lot going on here, and I will echo the others in that you'll really need to focus on yourself right now. Which I know doesn't help at all with the pain of what is going on with your wife, but the truth is, she's got her own struggles to contend with, ones that existed even prior to the affair. The affair will only make those worse most likely. But those are her burdens for now, and you are in no position to help her at the moment. So let's attach your airbag before helping others, if you know what I mean.
Here's a question for you... you said your wife struggled with alcohol prior to the A. Was she struggling with it when you first got married? If not, when did it start and how? The question I'm really coming to is this... Why do feel you allowed yourself to seek out and establish a relationship with someone so broken? If she wasn't broken to begin with, what happened, and again, why have you allowed it to continue? Did you feel like you weren't worth more? Or did you feel like her savior perhaps?
The answers aren't for me, they are for you, and your IC. To be clear, I'm not trying to toss any blame on your wife here, that's not my goal. Rather, I want you to start thinking about what factors in your life led to the affair. What boundaries did you cross, or did they not even exist? You seem to pick people and situations that tend to be broken or end poorly, and that reflects back on you, what you are willing to allow in your life, and what "normal" feels like to you, even if your normal is everyone else's "broken". See if there are any similarities in what attracted you to your wife that affected why you sought out an affair? What need were you trying to fill? What your sense of self-respect and dignity didn't kick in and prevent you from taking that path?
What will help your wife the most right now is you getting your head on straight, and making changes in your life that will ensure this never happens again in the future. That starts with understanding how and why you allowed this to happen, and then taking steps to correct those ideas.
Hang in there, this is the really tough part. Keep coming back, check in, let us know how you are doing and what's stressing on you.