Wow you must be strong to have been dealing with all that plus 3 young ones without having a nervous breakdown. That inner strength is one thing that will help you through this.

I agree with the suggestions for counselling - they'll help you sort out your thoughts and make a plan for what you need to do.

It's so hard to make the final step when you('ve) love(d) someone. You also care about their welfare so it's hard to say 'no, that's enough, it's time for me to put myself (and my children) FIRST'.

I'll try to look at the questions you've asked:

"will I be free from him ever?" - you'll always have a connection to him through your children, and so in many ways his problems will continue to affect you because they will affect your children, but they will do so in a much smaller and more distant way. For one thing he won't be part of your daily life (assuming that you'll be the primary carer, given his issues), so you won't be dealing with his problems on a day to day basis, and nor will your children. You'll be 'free' to make your own decisions, manage your own money, put yourself and the kids first, and move on from the pain, hurt and disappointment his behaviour has caused. His problems won't automatically be yours anymore.

"he said he's sorry for the way he's treated me (heard that before), he loves me (heard that before) he will change (heard that before)... why can't I let go and accept that it's over? why can't he?" - There's lots of reasons it's hard to make the final break, and these are why many people continue to live in unsatisfying relationships (which is just as valid a choice, as long as it's not unhealthy for the children). I would say that he can't let go and accept that it's over because deep down he doesn't want to lose his wife and children, even though he hasn't done the work he should have done to keep them. And I'd say for you, the reason why it's hard to let go and accept that it's over is because when you have children it's really damn hard to say 'this isn't working' and to make the brave decision to go it alone. You don't know what it will be like on your own, you've probably got fears and anxieties about the unknown, you don't want your children to have divorced parents. There's also the fact that you still care for him, and the fact that he's got problems and had a difficult life. It's hard to say 'I give up, I've done all I can'. This is where the counselling could help you sort through things and really feel ok with your decision.

"how do I keep on track and not back down again?" - I think the first step in this is really being sure of your decision, probably through counselling. Relationships Australia charge according to income so you might be able to get in quite cheap there. Or you could go to your MCHN for a referral to a community counsellor which should be free. Another way is through writing. Write down the reasons to stay and the reasons to leave. All of them. Even the tiny little silly reasons. Go through future scenarios, your self, your kids, every part of life that is/will be impacted by your decision. Look at ways you can solve any issues on your pro/con list, the support you'll have either way, housing, finances, transport, childcare, etc etc. If you're still unsure, talk it over with a trusted friend. That process should bring you to a point where you realise that one way or the other, your decision is the right one. Having thought through it so deeply you'll be more resolved in your decision. Also, what is it that makes you feel like backing down? Look at them all individually. If it's promises from DH that he will get better? "Ok then you need to prove it and I'm going to move out while you do" (or whatever it is that is satisfactory to you). Is it concern about managing financially? Give centrelink a call, find out what you're entitled to, and write a budget. And so on. Work through all the issues that make you feel like backing down. I think these processes will help.

Goodluck. Whatever happens, you'll be ok.