Khamenei insists U.S. sanctions must be lifted first before Iran returns to nuclear deal

We will not

Ok. Sanctions will remain.

The JCPOA contained a part setting out what each side was agreeing to do.

It also contained a part setting out what each side was allowed to do if the other side didn't do what it agreed to do.

Nowhere did it have a part saying that the side that didn't do what it agreed to could demand additional things of the side that did do what it agreed to, or demand it stop doing what it was allowed to do in response to the failure of the other party before they would consider trying to do what it agreed to.

PS, yes, the democratically elected government of Iran can't force the US (or the EU3) to stop waging economic war on it, but it can ask the ICJ to force the US (or the EU3) to pay it every cent that the economic war takes from Iran, plus interest, plus penalties.

And seeing that Obama had to stop waging economic war on Iran because the ICJ was ordering the US to pay what previous Presidents had taken from Iran, it would be symmetry if Biden had to stop waging economic war on Iran because the ICJ was ordering the US to pay what previous Presidents had taken from Iran, too.

This shouldn't be that hard to fix - everybody should just do what they have to do at the same time!

US takes down the sanctions; Iran reverses its uranium enrichment - at the same time sitting on the table. What's the problem?

American foreign policy in the Middle East does not come from Washington DC.

US takes down the sanctions; Iran reverses its uranium enrichment - at the same time sitting on the table. What's the problem?

Iran is much more belligerent than NK and China.

That has been proven by their actions around the world. The US has very little need for anything from Iran, so they have only the clout from other countries that want Iranian trade. Every missile, launched in anger, every proxy war they fight, fund, and equip against rivals in the middle east and around the world proves their malevolence.

And seeing that Obama had to stop waging economic war on Iran because the ICJ was ordering the US to pay what previous Presidents had taken from Iran

That is an outright fabrication. In 2018 the ICJ ruled the US has to lift sanctions on humanitarian goods and it was in 2019 the ICJ ruled Iran has a legitimate claim to money held by the US. These rulings came long after the US negotiated the Iran nuclear agreement and long after Mr. Obama had finished his second term of office. They were in fact in response to the Trump administration reneging on the Iran nuclear agreement.

US takes down the sanctions; Iran reverses its uranium enrichment - at the same time sitting on the table. What's the problem?

None of the parties involved trust any of the other parties to keep their word. There are simply too many advantages to be gained either from cheating or simply not having a treaty. The benefits to the US seem pretty vague and absent a very comprehensive inspection program that so far Iran has refused to allow the opportunities for Iran to cheat are manifold.