Cock ring should help, but wanted to reiterate the health issue. Make sure he has his blood pressure checked, and gets a full physical. Sometimes smokers have circulation issues which can prevent adequate blood flow. Erectile Dysfunction often indicates cardiopulmonary compromise, and while that may not be the case, it is better to err on the safe side and rule it out with a physician.
HTH, and glad to hear you talked about it. That's an important step.