Thoughtful post, but I think a couple of your questions are from a wrong perspective or premise.
“Dividing up our country would not have been good. Had the South won, would it have endured, or would Texas have eventually withdrawn from the Confederacy.”
Even if Texas withdrew, it would not necessarily preclude the end of the Confederacy, just as the southern states withdrawing from the Union would not have caused it to cease existence.
“Would the South have joined in with the North in fighting tyranny in WWI and WWII?”
I believe, if there were a Confederacy and a Union, the Union’s entry would follow that of the South’s, if at all.
The Isolationist movement in the years prior to Pearl Harbor was centered in the Midwest. The South was the least resistant region toward going to war in WWII. FDR encountered a lot of resistance from Southern Democrats over the New Deal, but his wartime preparations (such as Lend-Lease) got near unanimous Dixie backing.