Divorce Source: Is there hope?

New to the forum and is not like me to post on line like this, but I'm lost and confused with no one to turn to. Here's my story...
I've been married to my wife now for 4 years, but we've been in a relationship for about 8. We have two beautiful little girls, the youngest is almost 2yrs. We've had a good relationship, albeit not like it was when we first got together, but not terribly bad either. I'd say we've been getting along fine since we got married and not much has changed between us except for the parenting part now. We have issues, i'm sure like all marriages. We have the occassional arguement over what I consider to be pretty common stuff, like money and family (in-laws), and what shows to watch, etc. I guess we've both gotten comfortable with the situation and it's just been this way, I'm ok with it. Well about 4 months ago, things started to change. We went from having this comfortable marriage, to where we are now, which is my wife wants to seperate and divorce. In a span of about 4 months, my life has been turned upside down and I'm just totally confused. So what happened? Let me explain. In late April, i sensed that my wife was acting cold and distant. We've had discussions about being more intimate with each other and she kind of alluded that she's lost some of those feelings and she wasn't sure how to get them back or if she could. This really got the alarms sounding in my mind. Then when she started to act distant, I thought something must be up. I've never checked her emails or text messages before, but thought I should snoop a little. I know it's wrong, but something in my gut told me things are not right. Sure enough, I found a series of text conversations with another man that she had met at work and was carrying on a very emotional relationship via text saying all the things that you would expect two people who are falling for each other to be saying. I confronted her immediately, and while she got very deffensive and angry that I snooped, in the end, what I got out of it was she no longer has feelings for me and she does not love me that way anymore. She's sorry but she's only in this marriage for the sake of our kids. Over the next several months, we had a number of arguements over this incident, I may have pushed a little too much, but I never felt I got the appology that I felt I needed and did not really sense any remorse on her part. Then about a month ago, I met up with her at a kids restaurant where she was supposedly killing some time with the kids. When I got there, she was with another guys, who I happen to know from work (by the way, we work at the same company, this is where we met), and she said they just bumped into each other by chance. He was there with his two kids and they just sat together and the kids started to play. He's divorced recently in case you're wondering. My stomach immediately turned and I knew something was wrong with this scenario. They both acted very awkwardly and he left shortly after I got there. I confronted her about this being strange and again she went on the defensive. She actually got so upset with me for not believing this was just a coincidence that I actaully felt like an ass for accusing her. Still not feeling right, I did it again, I snooped. Got into her email and saw that the whole get together WAS pre-arranged and it was to be kept a secret from me because as she put it in her email to this guy, my husband is jealous and told him a whole bunch of stuff about me that's completely not true and made me look very bad like some sort of jealous possesive controlling husband, which I assure I am not. Then she went on to appologize for making things so awkward by inviting me there after to minimize the suspicion. Well again I confronted her and the same song and dance about how she's not happy with me, does not love me and does not have intimate feelings for me anymore. She assured me that he's just a friend and needed a distraction. Well, this friendship with this guy has recently turned out to be more. They've professed their feelings for one another and now my wife wants a divorce. In order to get a divorce we need to seperate for a year first. In order to seperate legally and get a divorce, there's about a million things that needs to be sorted out, most important of which is our kids. We own a home together, who should stay or go? Who do the kids go with? Can we afford a divorce? We're basically at a stale mate as to what to do next. In the mean time, we've agreed to continue doing what we're doing while we sort things out legally. I don't want a divorce. I love my wife dearly and don't want to break our family and hurt our children. She's gone from staying for the kids, to where she's now which is she absolutely wants a divorce and there's no hope for us, not even for the sake of the kids. But while we're sorting this mess out, what do I do? She acts like we're still married, we get along fine, pretty much the same we've been carrying on for the last several years, yet every second away from me, all she does is want to be with this guy. She's got me somehow to agree to let her carry on a relationship while were still together because her reasoning is what does it matter? We're splitting anyway. We just can't right now because it's complicated, but I don't want to end it with this guy. I want him in my life, even if it's just as a fried. She's assured my they're just friends right and will keep it this way untill we're seperated, which could be in 6 months or a year for all I know. But for now, Do I have to put up with her having phone conversations with this guy every night or going out to meet him every other night for coffee? I feel like this marriage is worth saving and I've completely been blind sided by this whole thing. I just don't know what to do. Do I give her the ultamatum and tell her that she can't have any dealings with him until we're officially seperated or what? Do I give her her space and hope she see's the light and gives this marriage another chance? My only concern is for our kids at this time. I want them to have a proper family and not be part of a statistic. I'm so angry right now that I almost want to just tell her to leave. If she wants to be with him so badly, then leave. I'll give her her divorce, but I'm going to fight for everything. I feel like I have a right to fight for the house and our kids and leave her out in the street. Don't know if that's how things work with a divorce, but given what she's done in the last several months, do I have the upper hand on her in divorce court? And if I do get awarded the kids, is that right of me? I know how much my kids love my wife and I would taking them away from her out of resentment. But I keep telling myself, why should I be the one to suffer? I don't want to end our marriage. I'm not the one that's found someone else and fallen for them. If she wants to end this, then that's her choice and she should have to be the one to make any sacrafices, not me. I have a home and 2 kids that I love, why should I have to give it up? In the end, somewhere inside of me, i'm still hopefull that we kind come to terms and stay married and work things out. Any adive would be greatlyl appreciated!!!