1. Texans ould have to kick out the National Guard and beef up Texas's State Militia.
2. Would Texas have a right to its own coastline, or would that still be considered US waters?
3. Instead of seceding, would it be possible, as a short term strategy, to try and get other states to combine together as a super-state? The downside is that the super-state would send fewer senators to congress, but would continue to send the same number of reps. Over time, if the super-state gets big enough, it may have a better chance to secede, or get better terms with feds via reformed legislation granting more rights to the states.
4. Whenever the issue of secession has come up the claim has been made that the US would still own all of the infrastructure in the state created by federal edict, e.g. federal highways, parks, etc. The claim is that the US might let Texas secede, but only if they paid for all the stuff they got from the feds. This number might be in the trillions. A case could be made that all of those projects were partially funded by Texans and that Texans help pay for federal infrastructure in the other 49 states, so its a wash. But if we're still talking about a peaceful secession, then I imagine the courts would argue in favor of the feds. So Texas might be encouraged to secede, and then decide not to because of the price tag.
Solution to the infrastructure repayment - tell the feds they don’t want it, so come take it back. Sit back and watch the fun when the Yankees try to foreclose on a road, or a building.
As for the backing of a Texas currency, what backs up US currency? The biggest problem I see with secession - unless other states join Texas - is how do you get rid of the enemy within (Austin, Houston, Dallas, etc. liberals)?