There is no way he should a) expect you to give up smoking and the computer at the same time and b) to give up the computer over smoking!!!!!
Smoking is a habit that will kill you and is expensive, being on the PC for 1.5 hrs a day won't. Plus if he's not home when you're on it, what's the problem? I feel as long as the kids are fed and looked after, they have clean clothes on, and the dishes are clean - why can't you have some "you" time once a day, or every second day.
My only addiction is the PC, and Dh has issues with it sometimes, but men have their addictions like Playstation, Xbox, watching sports etc, so why can't we have our "thing" too? It's my contact with the outside world when I'm stuck at home most of the day.
You've done sooo well to be smokefree for this long, don't give up now!!! 