It all seems quite a bit overblown to me. There's legal precedent for the President to take over a state's national guard and use federal troops to enforce a court order (see Brown v Board of Education):

"In September 1957, Arkansas governor Orval Faubus called out the Arkansas Army National Guard to block the entry of nine black students, later known as the "Little Rock Nine", after the desegregation of Little Rock Central High School. President Dwight D. Eisenhower responded by asserting federal control over the Arkansas National Guard and deploying troops from the U.S. Army's 101st Airborne Division stationed at Fort Campbell to ensure the black students could safely register for and attend classes. [...]" (Source: https://en.wikipedia.org/wiki/Brown_v._Board_of_Education)

The current wording of the Insurrection Act provision (which has been amended a few times since initial adoption), according to Wikipedia:

"Whenever the President considers that unlawful obstructions, combinations, or assemblages, or rebellion against the authority of the United States, make it impracticable to enforce the laws of the United States in any State by the ordinary course of judicial proceedings, he may call into Federal service such of the militia of any State, and use such of the armed forces, as he considers necessary to enforce those laws or to suppress the rebellion."

Just my $.02 but I'd guess either the feds back down or Texas does. Hopefully nobody gets trigger happy.