The term you're looking for is the "unconstitutional conditions doctrine" [1]. It's not black and white. But it will be difficult for Texas to argue that U.S. foreign policy vis-à-vis Israel is germane to soil volatility in the Gulf of Mexico.
[1] https://scholarlycommons.law.case.edu/cgi/viewcontent.cgi?ar...
If a person is aware that he/she is waiving their rights, and is not some accidental waiver, the government is not being deceptive or coercive, the person is free to reject the offer from the government without sanction, and the person waiving their right has the capacity to understand that they are doing - then there is no (generally) constitutional violation.
In the context of employment or government contracts, the government does not guarantee employment to every person. The fact that a potential employee (for example) may be impoverished and desperate for a paying job does not make the government’s conditions for the job coercive, unless the government specifically created the person’s unemployment.
Yes, it is. The government refusing to do business with you solely because of First Amendment-protected speech would be a clear interference with that right.
https://www.texastribune.org/2019/05/09/Texas-anti-boycott-i...
This is not unprecedented among states in the U.S. Many states have banned government work and travel to other states and countries due to policy issues.
https://apnews.com/article/california-florida-lifestyle-trav...
Not only will the US government refuse to do business with you, they'll charge you with a crime.