It's a long shot, but it could be worth bringing up the idea of an e-cigarette. As someone who smoked for a long time, I can tell you that some of them really aren't at all satisfying compared to actual cigarettes but others come pretty close as far as simulating the feel of smoking a cigarette. My husband agreed to quit with me when I quit a couple years ago but he could never quite give them up entirely... however, we found an inexpensive e-cigarette brand (NJoy) that he really likes so now I've got him smoking that instead of the occasional cigarette. They're hardly a "healthy" alternative since nicotine is still pretty bad for you (and your blood pressure), but at least they're LESS unhealthy and most importantly, there's no second-hand smoke.
Instead of asking him to give up real cigarettes completely in favor of e-cigs (which sounds very unappealing at first to a life-long smoker - trust me), I would try to talk him into a compromise where he replaces just 1-2 cigarettes a day with the e-cigarette. If you can get him to do that, then it may be possible to gradually nudge him to increase the amount of e-cigarette and reduce the actual cigarettes, at least when he's at home. Some second-hand smoke is better than tons, after all!
There's also a product out there (you can find it on Amazon and at other online retailers) called "smoke buddy" that you might ask him if he's willing to try out. You exhale the cigarette smoke into the smoke buddy and it filters the majority of the smoke and odor out of the air, greatly reducing the amount of second-hand smoke produced. It's basically a hand-held air purifier, from the looks of it.