With all due respect to a recent law school graduate and a yankee professor I've never met a serious person who doesn't think that the formal re-admittance of Texas after the civil war rendered any agreement before that moot.
Yeah, just what we need, more senators.
Having representation is the way the government runs, so having more of them and their voting power with our philosophy makes a lot of sense to me.
I have heard the argument before on whether we have retained the rights we had prior to the War between the North and South (Note: it was not a civil war like you said). There is no one I have ever met who has shown any legal documentation that this right was indeed taken away from this state. My father, who mastered in Texas history at Ut-Austin could not find such either.