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)?
Yankees? Oh, you mean Americans.
As for getting rid of the enemies within, all you have to do is organize a state police and a system of informants. Then you kick in the doors in the middle of the night and haul them all away to concentration camps.
You can run the camps...you know you want to.