There are two issues: manhood and father-hood. Treatment of manhood is easy i.e. injection of Sustanon up to the age of around 60 years. But fatherhood is tough and tricky area. Your line of treatment for fatherhood is correct. Get your testicular volume assessed by ultrasound, also S. testosterone both free and total semen analysis. These test shall indicate your chances of becoming a father. This treatment is carried out till family is complete and then replaced by injection of testosterone.