At the Visa officer’s discretion whether to overlook the 3 weeks. These days tough to get away with shortfalls but nobody can guarantee what will happen.
Would consider withdrawing the application and applying again. Drastic but seems the easiest option if there are no answers. The situation in Iran and risk of not returning home will always be an issue but has gotten worse.
Your boyfriend should show he can fund his own visit and has strong ties to return to his home country like longterm job, property, etc. Previous international travel history, especially to certain countries, also helps.
That is why we have economic immigration programs. It has never been easy to immigrate after 40 so not having an easy pathway to PR should have not been a surprise.
What are their home countries? Unless indicated that under increased security screening I would be contacting my MP to ensure it isn’t sitting in a pile somewhere.