The problem is "amicably." There is no way the federal gubmint is going to let a state secede. The War of Northern Aggression established that any state wishing to leave the Union would have to do so through force.
Actually, I cannot think of a single example of any sub-region or colony wishing to “amicably divorce” EVER having been allowed to leave peacefully. Killing and misery have always been part of the deal, because those in power never ever ever want to give up any significant portion of that control.
No. It didn’t. What it did establish is that disunion can not happen unilaterally. All states are party to the Union. All, or at least most, would have to be party to disunion. That could occur certainly by constitutional amendment, and perhaps by legislation or by a successful case brought by a state with the supreme court as original jurisdiction.