Regarding "didn't used to", it seems that although this spelling, if not exactly logical, is quite common, it is often considered incorrect, especially in AmE, athough the Chambers Pocket Guide to Good English 1985 (British) found it "unexceptionable". Cambridge takes a practical approach:
"Both forms are common, but many people consider the form with the final -d to be incorrect, and you should not use it in exams"
However, in this case the question is rather academic, as Duo isn't accepting "He didn't use to hate his wife" either. Reported.