Heartbroken and needing help!

[irishblessings]

Cat and TG - thank you for your thoughts and experiences. They are VERY helpful. I am trying to wrap myself around all of this. This profound soul searching required to keep my head above water - to keep breathing - is often times leaving me empty. I realize that I have not allowed myself or respected myself enough to establish a sense of self. I've completely avoided that.
When faced with H's infidelity the first time - I found a part of myself that I liked. I found I had strength to forgive / to accept my contributions to the problems in the marriage / the ability to recognize that a lifetime of good is not erased by a handful of bad. I never thought I would have the fortitude to handle it that way - I always thought it would be a deal-breaker.
This situation though is different. It is a culmination of lies, deceptions, insidious acts that I find myself trying to normalize and the fact is I have no control over any of it. H does not want me in his life as anything but a friend and keeper of the family. So it's not a question of me being able to "handle" it - it's not an option. It's a question of me being able to create something for myself and my kids that is as loving, honest, "clean" as possible - because that's what I need and what I believe is what my kids need in order to continue thriving.
I have a couple of logistical questions:
1. What do I say to people who ask what is going on? That H left or that WE separated? I don't know how to handle this. He still has not told a soul except one of his brothers.
2. Is it "normal" when going through this to "exit" the social scene for a while? I don't feel secure enough that I won't break down in public. Somedays at work I have to close my door or my secretary will redirect people so that I can regain my composure.
3. I am still having trouble determining what to tell my kids. The older ones are smart enough to ask questions because nothing they are hearing makes any sense. I am struggling with what the "truth" of my situation really is: MLC and Addiction? MLC? Addiction? I've given the girls some general stuff to read about MLC and they can see some of their dad's behavior in it - but the addiction side would be new to them. Do I share the addiction side with them? What if they find themselves in addictive modes / do they need to know that it is in the family? They know about my father's and brother and sister's addictions.
I hope I'm not sounding like an idiot! It's more of a stream of consciousness type of ruminating. Basically - I don't know what I'm doing! But I'm at least trying to pull myself together!