Definitely have sex every other day. Try charting your cycle to determine your most fertile days. Sperm can survive in your body for a few days, so it's in your best interest to have sex a few times right before you ovulate as well as during.
Try laying still for a few minutes after sex. His semen will still come out of you, but this might give the little guys more of a chance to get to where they're going, if you catch my drift.
And I know this isn't what you asked to hear, but I wouldn't be worried about smoking affecting his sperm count. I *would* worry about smoking affecting your pregnancy and baby. Secondhand smoke is extremely dangerous. I would urge him to cut back on his smoking and eventually try to quit. His health, yours, and your child's will all benefit from this. Even if he smokes exclusively outside, he should be thinking about the effect his eventual bad health will have on you and your child(ren) in the future. Sorry, just giving my two cents!
Good luck, hon, and happy baby-making! :)