Relocated the family and he dropped the bomb

[steady]

The last few days he has said over and over that I don't need to leave and move back, he can move out for a while. I think he finally realizes that the problem here is with HIM.

You're assuming here. Until he tells you the problem is him (of course it's you also because it takes two to make or break a R) and specifically what he thinks they are don't assume he's taken responsibility.

He has said he blames me for his brother's death, even if that is not right or justified.

This is immature. Suicide is no one's fault. It's the decision of the person doing it no matter what they give as the 'reason'. To say "I blame you even though it's not right or justified" is an unbelievable thing for an adult to say. Especially with the magnitude of what such a statement carries.

He is making a full mess of his whole life and not dealing with the issue at hand.

Nothing you can do about that except draw YOUR boundaries so you don't get caught up in the whirlwind that is his life.

If he moves out though, which is what he want to gain clarity, how will I trust him?

It's obvious you can't. And you won't.

How will I know if he decides to have OW here for a weekend if he doesn't live here.

You won't.

What stipulations do I put on him for me to remain down here while he looks within himself?

So far I have thought of this:
1. He must call her on speaker phone and completely end contact. Tell her he is getting a new phone number and that his wife has access to all his email accounts. He must block her on FB.

Didn't he jump through a similar hoop a few weeks ago and then started contact on a birthday? You can do this step but it doesn't secure anything.

2. He must start IC within 2 weeks.
3. We must start MC within one month (I think it would be good for him to go to IC first for a couple of sessions).

Ok. This is good. But only if he actually wants to work on the marriage. If he doesn't, he may still jump through these hoops and resent you for it.

One last point, he stopped contact with her as of Wed. morning and from what I can see on the phone bill he actually hasn't had contact - I don't have his email passwords right now though. So for once he actually took the initiative without me asking him and he emailed her and said not to contact him for "a few days". That is a slight difference from before.

Is it enough difference for you? From where I sit he's being a nilly willy. It's like a kid who won't let go of the candy bar because he's so afraid someone else is going to take it or it might get lost. If you don't push him with a strong boundary he'll keep playing this game of ping pong.

He probably should have emailed - "Please don't contact me until I sort out my life. I have a responsibility to be a mature adult and deal with my W and our M and make some decisions as to where that is going."

I'm a little nervous about actually moving back. To go up for a few weeks is one thing, but I worry about his safety once the moving truck would be taking me and the kids and the dog away for good. His brother committed suicide and I know that it can run in families. He has said that the girls wouldn't notice if he was living here or not, he's never seen them more than a few hours a week so it doesn't matter. So to me if he thinks we moved away and are moving on with our lives and they are 'fine', he has nothing left to stay here for.

MM you are not responsible for nor accountable for whatever your H chooses to do or not do. I can understand your trepidation because you have been married to a man who seems to put blame on you when it's not even warranted. ie: his brother's death.

You need to deal with this issue for your own personal freedom. It's a form of people pleasing and caretaking.