To the brink of Divorce

[ACJ]

I'm not in any way near to piecing my marriage back together. I have come here for some serious advice. For those of you who are not familiar with my sitch a brief synopsis follows:

Me 39
H 41
Married 18 years this year
Kids D16,S13,D10

June 2004 I kicked my H out after a straw that broke the camels back moment. He went to live with his cousin and within 24 hrs I regretted what I had done. He felt relieved. It took him a month to decide to come home but when he did he confessed to having a fling whilst he had been away. I was devastated but knew from the time apart that I loved him more than anything or anyone on earth and so agreed to work on things. We went to MC for 10 weeks which cost us a fortune but at the time we both felt it was worth it. At first it was difficult but I felt we were both working on it. Sex had always been an issue and at first it was a lot better but without realising it things slid back to how they were.
Fast forward to October 2005 I was just beginning to have complete trust in my H again. We went on holiday with the kids and we have always found these very stressful times. By most people's standards it would've been a bad holiday but by ours we had a great time. When we got off the plane H commented how he didn't want to be back but I just put that down to not wanting to go back to work etc etc. Everything was fine for a couple of weeks and then it began.
He was going out and not coming back til 5.20am several times a week and this was not like him. I asked if he was having another A and he said no he just needed his own space. So hard as it was i tried to give it to him but have to admit to loosing it more often than not. Finally I cracked. H teaches a karate class on a Wednesday night. This particular night he came home at 9.45pm and announced he was going to have a shower and then go out again for a drink with some of the guys from his class (he teaches adults). I was very unhappy by this but tried not to cause a fuss. At 6am the following morning he still was not home and I was ringing the hospitals to see if he had had an accident. 6.20am he rolled up in a taxi, very drunk and barely able to walk.
This could get very long so I will skip some detail. Suffice to say that I did not go to work that day. I took kids to school and noticed that in his drunken stupor he had left car keys out on stairs (something that he hadn't done for a while). So i snooped and wasn't prepared for what i found. Wrapped up birthday presents. One was a bottle of champagne, one a box of chocs and I don't know what the other was b/c for some reason i never opened it. This was mid nov 2005 and my birthday is in April! So i confronted him and it turned out this woman was 22 that day!
Again skipping details and moving forward a week. He left saying he wanted a trial separation. 2 weeks later he told me he had stopped seeing her. We spent a very painful xmas day together for the children. In between Xmas and NYear he told me he didn't think he was ever coming back. N Years Eve he told me he wanted to talk about splitting our finances. Mid January i noticed he had taken his wedding ring off. he had done this before but when i mentioned it he always pulled it out of his wallet and put it back on. this time he didn't and still hasn't. Found out a few days later that he was seeing antoher OW who it turns out was 25 on valentines day. She is from Czech republic and shares his passion for karate (which I don't).
Skipping a couple of months he know rarely looks after the children and if he does will not normally stay until I get home from work as he has to get back to her. He moved started staying with her on a more or less permanent basis virtually straight away as far as I can work out although his clothes etc have always remained at BILs.
On Mothers day we had a massive row (only one since he left) about money and he said for the first time that he wanted a D. Two weeks ago she moved to London as this was a planned move before they met. We live 300 miles away in the North of England. He told me several weeks earlier that he plans to continue their R even after she has moved so far away so that will take up all of his weekends. On 28th April he should take possession of a flat that he is buying. It is one bedroomed and his mortgage will be 4 times that of our 3 bedroom house! All he keep saying is that I need to get a full time job b/c he won't be able to afford to pay me anything other than maintenance after that. The weekend she moved to London I found out they were going to Amsterdam for a few days and so we did not see him for over a week until this Monday.
He came then to see the kids and I sat in my room reading a book so that he could have some time with them as it was clear he wasn't going to take them out. At one point he came upstairs and told me that soon we will need to meet to discuss a D. I told him I did not want a D but he said he did. I did all the good DBing things and agreed and validated what he was saying. We won't now see him for at least another week as he has gone back to London to spend Easter with OW.
So after this long preamble comes my question. Have any of you on this forum experienced something similar and if so how did you get back from the brink of D? I'm currently not initiating any contact with H but am responding to the little contact he makes with me b/c I know in general it will be about the kids. I know it is only a few days since he dropped the latest bombshell and i know I am not dealing with it well b/c I am on annual leave from work and so don't have my usual schedule to keep me busy. BIT I am literally going out of my mind with worry. I usually post in newcomers and everyone there has been very supportive but I feel I need the hindsight of people who have been there to help me avoid the pitfalls that must be there. I do not ever want a D and need to learn quickly how to avoid one. Please help me if you can.
Thanks