it's not about will. so many people have touched on great stuff (from a variety of angles), that i couldn't say much more, but i did have to speak to this issue of will.
most people tend to think that if they apply "will power" to something, then it will improve. they just need more of it. truth is, it's like tightening the lid on a pressure cooker--it only creates more pressure. and eventually, that pressure leads to an explosion. between Dh and I, we call this "it comes out sideways."
so, say someone has a perfectly acceptable and natural desire: desire for sexual satiation. but, something in the culture or mind of the individual says that however much that person has is "too much" and that they must apply "will power" to overcome that desire. it becomes about constraints and controls. only masturbate once a week; or no masturbation, only sex in marriage, and only when your partner feels that it is ok/right--so no more than twice a week. if you are thinking about it more than that, then stop thinking about it. *apply some will power.*
what happens is more pressure and more frustration. more frustration increases desire, and that leads to all kinds of craziness. in the example above, could be rather innocuous such as fantasizing or go the distance into sex addiction.
so, talking about these things in terms of will power isn't helpful. it only creates more pressure and frustration and leads to that energy 'coming out side ways' into food addictions, eating disorders, shame and frustration around food--rather than a truly healthy relationship with food (or sex, or cleanliness, or whatever).
so the reality of it is actually to *figure out what you truly want*. this is best described in Charles Eisenstein's book The Yoga of Eating. It's not a diet book, it's nto about how yoga practitioners eat. It's about relationships to eating and food.
Charles used to tell his university students "go out and drink as much as you want." all of the sudden taboos were off, pressures to "be good" were off. and what normally happened? kids would first go out and drink and drink and drink. then, something happened. somethign observational. they would come back to class and charles would say "how much did youw ant to drink this past weekend?" and a student would say "well, i thought i liked getting drunk, but then i realized i hate feeling sick and out of control. so, i thought maybe i didn't really want that. so, i really only had a couple of beers--a nice buzz and a good time, no sickness."
When i run a yoga retreat, i bring an excessive amount of chocolate. I cut it up (i buy it in big bulk chunks), and put it on a tray. i tell the students "you can have as much chocolate as you want on this retreat." what is interesting is that the "chocoholics" start out going pretty hard. lots of chocolate that first night. btu the next day, they want less. just a bit. and then the next day (usually the last of the retreat) they have a tiny square or none at all. and later, they say to me "it's so weird. i always used to say "oh, i can't have that. chocolate isn't good. no." and then i would eat a TON of it, but try to behave like i wasn't. then, you said "have all that you want." and you know what i realized? i didn't want all that much. i find that a little bit now and again is really satisfying. i eat when i want, as much as i want, without guilt or shame. and you know what? it's ok."
so the truth is, *something else* is going on--and you know this. it's not about food knowledge, it's about self knowledge and processing something via eating. you know this.
therefore, remove all of the pressure. not to say you don't guide, but just get out of the idea of pickin on him for food choices (tell DH to cut it out), and get out of the idea of restricting, educating, helping. figure out how to help him process whatever he needs to process, and make food unlimited and available.
he'll figure it out. and i do recommend the book. it goes into it much, much better than i can here.