The Constitution ain't a contract. It's a constitution.
The Constitution says, amongst other things:
1. The federal government has the right to regulate commerce among the states.
2. War powers are exclusively the province of the federal government. Including suppressing "insurrections". The state doesn't have the right to establish its own army.
3. Contracts Clause: "No State shall enter into any Treaty, Alliance, or Confederation . . . "
4. Import-export Clause: "No State shall, without the Consent of the Congress, lay any Imposts or Duties on Imports or Exports, except what may be absolutely necessary for executing it's [sic] inspection Laws: and the net Produce of all Duties and Imposts, laid by any State on Imports or Exports, shall be for the Use of the Treasury of the United States"
5. Compact Clause: "No State shall, without the Consent of Congress . . . keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.
6. Treason: against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. Presumably, anyone who is trying to take land away from the US is an enemy.
7. Federal Property Clause: "The Congress shall have power to dispose of and make all needful Rules and Regulations respecting the Territory or other Property belonging to the United States." Therefore any federal property in Texas or anywhere else is the feds, and the state has no right to make rules regarding it.
8. Supremacy Clause: "This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding."
9. The Oath Clause "The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution". The state legislature is oath-bound to protect and defend the Constitution. Not revoke it.
So here are just some parts where the states no longer have the right to do something that a sovereign nation would do, and no remedy besides Constitutional Amendment to get any of that authority back. In constrast, there is no mention whatsoever of a state being able to leave the Union. From that, it should be fairly obvious that a State can't just decide it doesn't have to follow the Constitution anymore and can be its own, separate nation without the consent of the sovereign which holds all those powers the states gave it.
Dealing with your first concern, states, unlike people, don't die. The states joined the club. They are still the same states they were then. This isn't a case of people being bound by their ancestors decisions, this a case of a sovereign entity willingly giving up the portion of its sovereignty which makes it an independent nation. If you don't want to be an American, you are free to leave and renounce your citizenship. The states though are bound to the Constitution with no right of revocation absent constitutional amendment.