According to Judge Roy Moore, the Rule of Law is the Constitution itself.
Therefore, according to the Rule of Law, Jeb Bush is empowered to rescue Terri by Article 1, Section 2, of the Florida State Constitution.
Others have also agreed that the Constitution gives this power to the Governor, such as Dr. Alan Keyes, and the Thomas More Law Center.
As far as principles go, life trumps them all, because the law has the promotion of life as its purpose and end.
Your points are well taken and I agree with them. Therein lies the problem. Many Republican FReepers don't like Roy Moore, Alan Keyes and probably not the Thomas More Law Center either. As hard as it is for them to approve of the government starving Terri to death the cult of personality is greater than the Constitution or natural rights in their eyes. The people you quote must be wrong or else the Bushes would be wrong and that can't be.
I should also have said: rescue of Terri by the EXECUTIVE branch would not only NOT harm the RULE of LAW but would in fact protect it.