This is the simple strategy.
Maintain the embargo.
Iran leadership cannot survive that. It is slow but it does work.
Iran’s CPI is running in the mid-80% range YoY. That’s high enough to cause some financial pain and economic dislocation. But they are capable of enduring enormous hardship and cannot apply any meaningful political pressure on their leadership. What seems intolerable to us doesn’t have the same effect on countries more accustomed to deprivation.