How might the trail of tears actually have saved the peoples of the “five civilized tribes” from complete demise?

The trail of Tears forced the tribes to move, allowing a small portion to move to land were the population could go and restart. Whereas if there was no trail, and the tribes stayed where the were, this would have potentially led to more war between the colonists and the Native Americans, leading to the possible decimation of the "Five Civilized Tribes". Good luck.

b. parliament was weaker than the monarchy.

whats the question? im not quite understanding your question.