Ok, the first focus with Mexico (or really any state that isn't the UK) is education. Set it all the way to the right and lock it by double clicking. VIPeR has some nasty criminals that might take fending off, but the main thing to realize is that crime funding should go to 0, 50 or 100% and that half-measures in between are mostly a waste of cash, iirc.
You don't want to go at 50% or higher on your taxes for a number of reasons - set your taxes to 49 point whatever (22, I think) - anyhow, whatever is just under 50. Lock those by double clicking.
Set your tariffs as high as you can (your screenshot says you can go to 100% - go ahead.) Then go through your provinces and split any POPs larger than 40k - each one will be less efficient on their own but your RGOs and factories will be more efficient for having more workers.
At that point you should be fine - expect to run a little in the red during wars if you want to win them and crush the Texans as fast as possible, being sure to use a cav unit to pick up their claims.
Alliances with the UK or France might help make the US think twice about DOWing you over the West, but otherwise you might have to keep a sizeable standing army, which would be unfortunate. If you have to keep it anyway, use it to bully your neighbors to the south and east into paying protection.
Don't use this on Texas, though, since they'll just integrate into the US and you won't get anything; and don't satellite any of them, since you won't get any resources or cash and you won't be able to DOW them again.
The last thing would be to click the largest capi you've got, making sure he has 100% of his necessary and everyday goods paid for, and run the clock a little to make sure he's accumulating cash. If he is, you'll start getting free railroads and factories in the future; if he's not, you need to ease off his taxes and the tariffs as much as you can afford to allow him to pay for everything.