A couple things.
If he's interested in TRT, it may be an in for you to demonstrate what the smoking is doing to him, in terms of trading something he's already doing (smoking) for what he now wants (perceived benefit of higher testosterone levels).
He will need to get blood (or saliva) hormone tests and likely some other blood panels. I'm guessing he's not one for frequent doctor visits (smokers generally aren't). This could be the first step to showing him the cumulative effects of his habit.
First thing, and possibly the best thing overall, for his health will be things to help oxygenate and distribute bloodflow where it is needed. If he's ever needed something like Viagra, this is an obvious example there are blood flow issues. There are herbal/nutrient combos that can do this.
At least get him on a good dose of fish oil, maybe even some of that Toco-8 vitamin E first. If he won't do that, I wouldn't go much further with it.