Our OP mentions that he and his fiancee have extensive CC debt. There's no question then as a practical matter that paying off the CC debt is the right move financially (the CC debt is at far higher interest) and also in terms of their credit score (lowering CC utilization improves scores far more than lowering installment debt).
People have asked in the past whether it might be possible that loans in deferment might be ignored by FICO 8. What seems fairly certain is that they'd still affect your age-related scoring factors, but I suppose there is a chance that the developers might have designed the model to ignore the amount owed while the loans were in deferment, which affects something called installment utilization.
If one of them wanted to test this for the benefit of the community here, we can suggest a way to do that, once their CC debt was paid off. But they shouldn't get their hopes up. The results of the test most likely would show that the debt is being counted just as much as if it were not in deferment.
