The question of curability of impotence is not a relevant consideration for the purposes of section 12 of HMA. Where a medical expert has found less than 50% of erection after the "pipe test" in the male s*xual organ such male can be treated as impotent for the purposes of this section.
Impotency in matrimonial cases means incapacity to consummate the marriage, i.e., incapacity to perform conjugal intercourse with the spouse. The word 'impotency' has not been defined in the Hindu Marriage Act but it has been made a ground for getting the marriage annulled if the same is not consummated owing to the impotence of the respondent - spouse. In order to consummate marriage a normal s*xual intercourse must take place, but the degree of s*xual satisfaction obtained by parties from each other is not relevant. Where complete coitus is established, the discharge of semen in wife's body is not necessary condition of consummation.
Thus as suggested by expert advocates, though it is more than 6 years after, on the basis of your efforts for treatment to him all the while, which failed to yield desired result, your grounds for annulment for marriage stands justified.