Partner troubles!

I'm in the process of preparing to TTC, I've come off birth control and I'm taking my prenatal vitamins and trying to lose some weight in order to lower my BMI and be in the best health possible for conception.  The only problem is that my SO is a smoker and drinker.  He has eased off the alcohol recently but he is not prepared to quit either completely. He has a 15 year old son and thinks that because he is fine that our future children will be but he doesn't seem to understand how much time has passed since!  I have tried to research how your partners health can affect a baby but I've not had much luck other than it can damage the quality of his sperm although doesn't say whether that itself affects an unborn baby.  I was just looking for some advice on whether my SO will drastically affect our unborn child (i.e will it be more likely to be born with defects/disabled?), I know it isn't the end of the world if it is but this is my first so I'd rather have the healthiest baby possible, don't want to offend anyone by saying that.  Any help would be greatly appreciated.  I don't have any intention of nagging him to stop, I've tried and it just ends in arguments :(