My heart goes out to you during this really hard time.
Whether he can lick the drugs or not is outside of your control and it sounds like you have enough to deal with just putting your life back together. First, consider getting off the roller coaster. My experience with my addict is that if I follow her actions I am up and down and sideways every day - it's exhausting! He is an adult and responsible for himself and obviously he knows how to get help.
I know what it's like to fear the worst - and then have a lot of it come true. I came to realize that if I could find peace with what might be the worst outcome, I could free myself. I know that sounds really hard. If you can release your husband to his HP, you might be able to free yourself. In the end, you can't save him, he has to do that.
Also, I mentor a child of a single mom who went through a lot of hard times. She doesn't have a lot of marketable skills but what she HAS done is really educate herself in terms of all the support she can get from whereever she can get it. She works a couple of part time jobs to make ends meet but keeps her hours low so she can be there for her kids. Beyond her work, she's not too proud to accept help from the county, children's services, etc.
If you need additional support, you may want to start by calling around. You could start with your county social services. They often know how to get debt relief, job training, etc. Another thing I tried with my niece is to call some local women's shelters. While you might not be ready for that, they also know of other support services you might qualify for that could help. There are also things like crisis nurseries or big brother/big sister organizations (when you just need a break from the kids and they benefit from some good role models - the one I mentor for is called Kinship), and there are also church organizations, etc. If you're not afraid to go down a few blind alleys, there is a lot of help out there.
I am amazed at how the mother of my mentor child has put together a very good life for herself and her kids because she reaches out to whomever and wherever she can to get for herself and her kids the help they need. I think she is a great mom in this way.
Lastly, I don't have experience with Methodone, but a friend of mine has a brother on it. He is concerned about his brother because he tells me that methodone is a narcotic and that his brother is "spacey" on it. I don't know if there is a viable alternative - if your husband was doing heroine, I know it is very hard to kick. Even if he stays on the methodone, he's a long way from out of the woods.
Prayers that your HP shows you the way.