If you're filing based on your having been a green card holder for more than five years, it's okay if you put "unknown "for your husband's date of naturalization. It would also be okay to put "cannot be determined at this time" . You can either attach an addendum to form N-400 explaining, or explain in person during the interview That your husband is withholding that information from you, because you suspect he does not want you to become a citizen.
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If you are filing based on 5 yrs LPR it should be fine writing info about your husband as unknown. Also attachan explanation and underscore you are applyingbased on your 5yr time asan LPR