Well, you've outlined the problem in the West. As history saw, the Confederate government didn't come up with a solution for it -- didn't even try hard, until Chickamauga, to effect some check to the Union's progress.
And as I said, significant resources sat idle in Texas, protecting rice and sugar-cane fields.
I would disagree that the south didn't even try, they just kept getting whipped. At Iuka, at Perryville, at Stone River, at Shiloh, at Memphis and New Orleans and Fort Donalson, The south had too much border to defend and too few troops and competent leaders to defend it.