Can my husband ex-wife allegations to USCIS about me block me from obtaining a green card?

Your husband's ex does not have any legal standing in the eyes of the USCIS. Only your husband, the petitioner, has. However, they may inquire from the both of you these alleged new information to be clarified. But as long as this has nothing to do with the criteria for the approval/denial of your LPR, it will not matter.