Well, I wasn't in a similar experience, but in my own experience, I only left when he made it clear that he was unwilling to work on anything with me. To me, that means there's no point in beating my head against the wall any more.
I don't know your whole story, but from what you've written here I would encourage you to talk to his doctor (it's even better if the doc you see is the same one he sees). Tell him/her your concerns about your hubby being addicted to the pain-meds.
I can tell you, you can live with a LOT of pain without meds. I did every day for 3 1/2 years while I was pregnant and breastfeeding my youngest son. I just recently have been able to take my meds again. I've been living with the pain of herniated discs, damaged nerves and muscle spasms for years without meds (and that doesn't account for my migraines). I know this is a lot of info about me, but my point is that if your hubby is claiming to NEED the pills so badly that he can't wait for the insurance, then he is addicted. An addiction is a medical issue. He needs help.
Talk to his doctor (the doc should be switching him to different meds to break the addiction to the current ones and keep switching/lower doses to wean him off, he should also get a consult to a pain-management clinic which can help with other forms of relief), talk to his side of the family and those on your side that care about him. Talk to a social worker and ask about resources to help with an intervention. He needs your love and help now more than ever. Even if you feel disgusted by him, please don't allow your son to watch his own father self-destruct. Show your son that you care enough about your family to get his dad the help he needs to get over his addiction.
Drag him to a Narcotics Anonymous meeting if nothing else. Most painkillers are categorized as "narcotics" so he can meet other people addicted to the same meds he's on. Speak to him about the effects his addiction is having on your son and your marriage. Tell him that you love him and you want your life together back. Be firm but supportive.
Please don't bail just because he needs help with an addiction. I personally wouldn't bail unless he refused to admit that he has a problem (and I mean persistently, some denial is normal). If he refuses all help and refuses to see what it's doing to your family, then it's time to talk about a separation.