You are doing the right thing. In fact, when you love an addict, the best thing to do for them is to pull back and let them fall on their faces and deal with the consequences of their actions. It sounds like they have a dream life for a drug addict. I am a recovered addict, and if someone paid for my house, car, and I got money whenever I needed it without working I would never have gone into recovery. In fact, with unlimited money, I would be dead.
You are acting like a reasonable, healthy person with strong boundaries. Your wife might love her children, but you can not love addiction out of people. It seems like you have a good grip on what needs to be done, I pray that your wife reaches out to counselors and support groups and is able to see that what she is doing is making them sicker, not better.
You and your wife deserve to be happy. Unfortunately, she sees her sons has helpless little boys, even though they are grown men. I hope it doesn't have to end in divorce, but you need to do what is right for you.