I can definitely sympathize with what you're saying and where you're coming from. The thing you have to understand is that your husband is an addict. This isn't a habit, it's an addiction. That's what keeps him going through two cans a day while he presumably watches his dad die a slow, painful death as a result of dipping.
Ultimately, it will be up to your husband to decide when he's finally had enough. No amount of nagging, pleading, or threatening will make him quit. He has to want it for himself. That's the bad news. The good news is that once he feels like he has arrived at a place where he knows he wants to quit, but either doesn't know how or is scared of what that means, that's where we can help.
My advice to you is twofold:
1) Write your husband a letter. Tell him exactly what sort of impact his nicotine addiction is having on you and your family. Tell him your fears. Tell him what you told us - that you want him around for years to come. Don't threaten or nag. Just be direct and honest.
2) Tell him to come here and poke around when and if he decides he wants to quit. Have him get in touch with me directly, and I'd be more than happy to get him pointed in the right direction in terms of posting roll, jumping in with his new quit group, and getting engaged with his fellow quit brothers on here. If your husband is a man of his word and is willing to take his quit one day at a time, this place will absolutely help him to save his own life.
Finally, you're a good wife. No matter what, he should feel proud and humbled to have someone that cares as deeply for him as you do. I hope for his sake and yours that he gets done with being a slave to weed sooner rather than later.