U need to calculate all ships not just oil, so include LNG, cargo etc
$15bn is only for oil
U also need to calculate the fact that the pre war oil money Iran receive is not profit but revenue. There is a cost for getting oil out, moving it, paying wages, maintaining all the equipment etc.
Toll is almost all pure profit.
When I calculated it worked out similar.
And with anything the ideal situation is some pay and some don't so U have some leverage over global markets whilst also generating an income.
Nukes are nice, having them gives u deterrence and helps control the escalation ladder but I don't think it would have stopped USA and Israel attacking Iran.
When Israel attacked Iran in 12 day war, what would Iran have said, "ok now we gonna nuke U guys?" Or when they joint attacked then this year? No they wouldn't, because Iran knows it too would get nukes.
Generally no country will use nukes on the onset of war, only if they get super desperate. But like I said it defiently helps having them, puts U in position of power
Iran is currently partially closing it, potentially making money and normalising it.
If in future Arabs find ways around it, Iran can bomb them pipes/pumping stations.