Will the age difference be a problem at interview if I file a petition for him to register for permanent residency?

There is no statute or regulation that makes the age difference you mentioned an impediment to a successful adjustment of status application, but you correctly recognize that such a large age difference can be expected to lead a USCIS adjudicating officer to be suspicious about whether you your husband live together in a bona fide marriage. You should expect a heightened level of scrutiny in the application process, including a requirement that you supply a particularly strong set of supporting documents to prove the bona fide nature of your relationship. Of course, there are many additional details that determine immigration eligibility. It would be wise for you and your fiance to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.