[cptaj]

I havent done the numbers but you are probably right.

Orbits are very unintuitive things. For starters they're much higher than a suborbital trajectory.

You would also need to pre-target to stage in orbit and at that point you're locked into that trajectory unless you brought A LOT of extra fuel. This would inevitably be slower and less flexible regardless.

The only way for this to have any advantage is to stage a ton of nukes in orbit at different trajectories, which is politically insane.