I would start with talking -- maybe at a group session or counseling. He needs to understand that what he is doing is hurting you, and there are probably some things that he needs you to understand too.
If you can make it look like you are doing this for me it might be a better approach. It sounds like you are trying to get him to come along on your Primal journey because it has done such a good thing for you, and you want him to be healthy too. It sounds like it's not something he's interested in doing for himself, because as you said, he enjoys his lifestyle the way it is. But if you can communicate that it's something that would make you very happy, do it for the sake of loving you and so on, it could be a place to start. Even walking for 10 minutes a day could make a difference, say it's something you want to do for 'alone time' with him where you can just chat without the distractions of the world (hard to chat in a car, or near a TV set).
And I will say again, communicating this to him is very important. Appeal to his best person, he probably doesn't know that it is hurting you or worrying you. Some people are not future-thinkers and don't consider this stuff, so people like you need to remind them, they will otherwise just do short-term decisions without thinking of the long run. I also say this because this is a public forum, and although unlikely, it is possible that he may see these posts. It is always better to hear about a problem from the 'horse's mouth' rather than finding out through someone else, and with the public forum it would be like you are talking to everyone but him. He might feel singled out.
Who knows? I don't know enough about your situation or the people involved, but these are just some of my ideas.
Stumbled into Primal due to food allergies, and subsequent elimination of non-primal foods.
Start Gluten-Free/Soy-Free: December 2012; start weight 158lbs, Ladies size 6
Start Primal: March 2013, start weight 150lbs, Ladies size 6
Current: 132lbs, Ladies size 2
26lbs lost since cutting the crap.