Hi,
Welcome to the ehealthforum and I am glad to help you out. The normal sperm concentration is greater the 40 million per ml and 70% of the sperm should be mobile with a very active forward progression. In your husband's case, varicocele, can be responsible for a low sperm count and hence infertility. So it needs immediate surgery.
A recent study shows that sperm count can be improved by a combination of zinc, vitamin C and folic acid. In addition he should stay away from getting the sacs overheated like that caused by tight underwear, long stays in a sauna or Jacuzzi or overexercising.
I sincerely hope that helps. Take care.