It sounds to me that you have your head screwed on the right way
I don't know how old you are but i am assuming late 20's, both of you.
It certainly sounds like he has a dream, one that he can't fullfill and it's not because of you... Ambitious people work around things and make life as happy as possible for those who are in it, whilst working towards their dreams.
If, un-happy in themselves, they have no alternative but to put the blame on the other person... It's their defence.. It's how they can justify and they are always right and you are always wrong.
The children are and have suffered from this on-going cycle, as you say, you've kept a diary since 2000... and you have tried in your way, to find ways to make him happier but to no avail. The children are emotional over his non support to them, and can't wait to see you as they crave for the love that they are not getting. You also i suspect..
This appears to be an on-going problem, an on-going battle for you and one that i don't believe you can change.
Drugs aside. Your husband found an interest. The wargames, from this he found connections, one in particular and chatted away, laughed etc. He is not responsible, he does not comprehend marriage, children and all that goes with it. He is more than likely a batchelor whom can't cross over to what it takes to be married and have children.
My ex-husband was obsessed with motor bikes, and cars. As such, there were rooms i could never go into, garages i could never park my car in, whilst he consumed all of those areas.. Three motor bikes, 2 motor cars and around 600 toy ones, displayed even in the house. Obsessed. Much like yours is with boxing..
The DVD's we watched were cars/bikes/Formula1... I never watched a chick flick, or got the chance to choose one, he would return home with horror ahhhh... Scary...
He obsessed so much that i became a cook and cleaner. Even if we had guests, he'd show up half an hour after they arrived, having been on the bike with mates. Yet, i needed the BBQ cleaned, ice etc..
On weekends, he'd be sorry, i'm going for a bike ride with .... every weekend... Batchelor.. In the end, he stated, i'll be doing this until i'm old, better get used to it.
Basically, what i am saying, is no... there are responsibilities in a marriage, it's an equal thing with both having hobbies for sure, be it playing computer games, or riding a motor bike. But, if they can't fit into the marriage scenario they never will. I stayed 7 and a half years and there was more involved, as to why, as in, same as you, it's my fault, i work to much, it's my fault, for everything, verbal abuse commenced and that was my fault to, cleaning the fridge the wrong way, my fault it's scratched, etc i walked. It wasn't my fault.
In fact, it was simple. He was a batchelor, and he'll always be a batchelor.
Your husband's a batchelor. He can't fathom the commitment involved in marriage full stop.
No doubt there are issues from his childhood that reflect in this.
Bottom line is you are not happy, you say you could be with him, but you have never been, you've written a journal helping you through it all for 8 years.
Your children are not happy, they cry, they are left alone, your lucky that they haven't walked out of the house onto the street, whilst in his care.
He is who he is. He can not change.
I'm again so sorry he needs to grow up and learn responsibilities and he needs to stand by you at this point in your life, as rcoreyus stated, without a doubt... It's shameful.
But, i think, you need to see what your family and friends can do to help whilst you finish school and stand on your own two feet.
Don't believe that you won't find some loving guy out there that will be there for you and the children, because you will.
You deserve happiness, not constant negativity, blame and more importantly, no suppport for you and your children, no love.. Your children deserve a father figure, not someone who ignores them and leaves them on their own, to only cry when you get home.
Let him stay out of your life.
Stop thinking he's worth it.
Because he is not.
And, don't believe he can change as your as so nice and therefore, he has to... He will not.
Look after yourself and your children and finish your school and get a new life, one you and your babies deserve.
CW